Yeah if the DLC is regular then there is a lot less to worry about as the list could be expanded pretty quickly. The history of the series has shown their track list grows at a crawl though, so I think that's why many are concerned with the size of the track list and some of the well-known tracks that aren't very good being so high in the voting. If we are going to get 2 tracks a year or something, then people will likely be much more critical of the choices than if we get 4 or something.
I think "filling out" the track list, as in getting tracks that add unique experiences and unique locations, is the most important part. The series has lacked street circuits, really lacked good short tracks that aren't just amputated sections of bigger tracks (Lime Rock being basically the only one), and no tracks from Canada, South America, and very little representation from Asia. It does look like they are starting to fill in a few of those gaps though.
Losing so many tracks, for me, is the biggest concern right now. I do 99% of my Forza driving in league race stuff, and we are pretty desperate for new tracks even with the 30-ish useable tracks we have in FM7 now, so losing a big chunk of those and only get 5 new ones to replace them, a lot of people on that side of the community are concerned.