I did some extra "research" about it, forgetting the Tokyo theory and I decided to do some mapping work. Here are some points to be considered first:
1) The track maps we see on the internet are not on the same scale. All maps shown in this topic have SSR5 and SSR11 way too big or SSR7 way too small.
2) Using the images of SSR11 featuring the bridge of SSR7 outside, there are only two possibilities: SSR11 is on the left side of the bridge OR on the right side of the bridge.
3) I think that nobody of us really had a special look on SSR7. It features only one exit, the first close curve of the circuit. The other side is just a place where the highway expands to the tool booth, and PD put some walls to transform it into a return. There are three things to say about this:
(a) There is only one way out and SSR5 joins SSR7 through there.
(b) SSR5 joins in an entrance outside SSR7 map, but still on SSR7 highway. However, mapping shows that this is very unlikely (remember that SSR11 is close to the bridge).
(c) PD were on a hurry to finish the track and cut the SSR5 entrance, because it would just be an unnecessary detail.
You can clearly see point 3 by glitching at GT5/GT6 and entering "inside" SSR7. With that the whole map can be explored, with some extra details. Also, you can distance yourself from the bridge from outside map and try to look for the SSR11 view. There is a video glitching and exploring a little bit here:
Im sorry for my bad photoshoping skills and that the final map is ugly and with a bit poor resolution/definition, but at least it is practical. If somebody wants to do a pretty and "resoluted" version feel free to do so. SSR5+SSR11 map where re-sized and rotated several times and lost quality on the way.
I considered and put all the two possibilities, right and left, and considered the bridge position.
View attachment 488653
EDIT: The two red lines on SSR7 highway is the bridge.
I used maps from wikia.com, resizing only SSR5+SSR11 and keeping SSR7 and the same resolution. I also cut the other side of SSR7 lane (since it was distorting the map) and shrink the map on vertical a little bit, so it would be more alike SSR7 maps on in-game mini map. I considered that SSR5 straight measures 0.7 km, considered that the junctions of SSR5 and SSR11 were equal on size so I could have a reference for SSR11, and considered that the distance in straight line between one end and another end of SSR7 is about 10.14 km (SSR7 lap is supposed to be 23.28 km long, so the highway has about 11.64 km. I considered that 1.5 km are extra size because of curves).
These points are considered after mapping:
(1) It is unlikely that the 2 towers featured on SSR7 are the same featured on SSR11.
(2) There is a whole new circuit between SSR7 first entrance and SSR5, which suggests a second circuit or at least an avenue there. If PD did not cut the SSR5 entrance in GT5s and GT6s SSR7 circuit, the way between SSR5 and SSR7 is big and measures at least 2 km.
Im still a bit confused because mapping results are a bit strange. SSR5 is a bit too far from the way out from SSR7, however, if we put SSR5 close to the way out of SSR7, then SSR11 would be too much far from the bridge.
Im starting to think that PD didnt took this "easter egg" serioursly and made some mistakes along the way. Or maybe this is the reason that they took the connection from SSR5 to SSR11 out on GT5/GT6, so SSR5 could be moved closer to SSR7 exit (however putting an extra exit on SSR7 would be a much reasonable solution).
EDIT: I know that SSR5-SSR11 looks small. Even if I made a mistake on the sizes, it wasnt a huge one. The reality is that SSR7 is very long and big compared to SSR5. Just think about how big is SSR7 tunnel when compared to SSR5 straight.
EDIT2: I was in a lunch and a strange theory appeared in my head. A possibility, actually... Conspiracy, maybe?I dont know but it is worth sharing.
Maybe they did plan from GT1 on having a SSR City, and creating the main route. So, they put the SSR5 with SSR11 and were planning to put more.
However, they overestimated the popularity of SSRs. At the development of GT2, receiving feedback from GT1, they noticed that the SSRs were not that popular.
So they decided to keep SSR5 and take SSR11 out of GT2. However, they kept hope.
They kept carried their hope to GT3, made SSR11 a return, and decided that they would put another SSR track in GT4 and feature its bridge on GT3 at SSR11, showing that they didnt give up their project. However, the feedback from GT3 told them that SSRs city were still unpopular, and they decided to put others city tracks in New York, Hong Kong, etc... in GT4 instead of bringing the SSR track with the bridge.
Time passed and things changed. New tendencies appeared. They covered their feedback from GT4. So, hopeless, they decided to give SSRs a whole new purpose. Some of you guys know "Forza Horizon", right? Maybe they decided at GT5 development that they would create their own "Arcade game" in the future, using car models and fame from Gran Turismo. An specie of "Gran Turismo Horizon". So, they decided that the city of their "arcade game" would be based on Tokyo (coming from PD, that should be obvious), would have that japanese nonlegal racing style. And since the SSRs were already featuring Tokyo somehow (their bridge at SSR11 in GT3 were a copy from a Tokyo´s bridge), they decided that the SSRs would be the starting point of their "GT Horizon" city, since they were based on Tokyo and that they were at GT Series since the beginning. And because they would have their SSR City in the end, even with few people caring about. And for that reason they decided to put a street car going over the streets and highways of Tokyo at the ending of GT5´s credit.
So, they took their original project for the SSRs track with a bridge, and changed it. It was supposed to be a medium track, average track, but, instead, they decided that SSR7 was going to be one of the most important highway of the "GT Horizon" city, and expanded its layout. But since they didnt have any clue when "GT Horizon" would be released, and they didnt knew the size of their "Arcade Game" city, they decided to not put the end neither the start of the Highway, so they would be free for expanding it. And they also noticed that their city should have an airport, and decided to put the airport sign on SSR5 and create an SSR5 entrance to SSR7.
Why am I thinking that?
The surroundings of SSR7 are way too big for creating an Special Stage Route City. We could surround it with 10-20 SSR5´s if we wanted to. If SSRs arent popular, why creating room for literally dozens of them? If they decided to put a complementary free roam on GT, why would be that big? Too much big detailed place would take away their efforts to others tracks.
SSR7 was only introduced on GT5. Before that, things were small. 2 years later, Forza Horizon appeared. T10 probably had the same idea, but decided to execute first. I know I can be wrong, but this would make more sense and would be an answer to everything about SSR CIty.