I doubt any pressure (and exactly what pressure? a couple of people discussing the pro's and cons of it on a forum?) has an effect at all given it's already a dead certain they'll be included in GT6.
As for GT7 on the PS4 however, that's still some years away, with no backward compatibility they don't have to fear people sticking to previous games (which I suspect is one of the reasons they're still included, having less cars on a successor on the same console would also be a first for GT) making it easier to include less cars (just like GT3 started all over again) but all Premium quality (just like all GT3 and GT4 cars were all PS2 quality).
That's unavoidable obviously, sooner or later they will be removed (the car models as in ingame models, not necessarily the cars as some of them will be remodelled whilst others won't) so I'm not getting what the big deal is really or what those opposing Standards have to do with it, it will happen regardless of what anyone here says.
I simply wished they weren't included in the first place (GT5 that is) which in itself was the odd and unlikely part, not us complaining about it (which again didn't make a difference so you can still enjoy PS2 cars on the PS3 but don't assume you still can on the PS4 which hopefully gives them plenty of time to enlarge the Premium car list to an extend you won't even miss them).