I don't get this whole discussion, seriously... I don't care what T10 removed when going from FM2 to FM3. As a package, FM3 was still friggin' good. To me, better than any other racong game I've had until Shift 2 game out - which is the first to actually fully replace FM3 for me. And that's after playing FM3 for over a year straight.
I don't know what you had to expect in order to be disappointed by FM3, nor do I care in particular. No game's been perfect so far, but as a package, some game somewhat close to what would be the be-all, end-all racing game for me. If FM4 gets even a little bit closer to that than Shift 2 and/or FM3 were, than it'll be pretty darn good.
And as far as I am concerned, I'm willing to believe that T10 will pull that off. It's not going to be the definitiv racing game, but then again, S2U isn't the 'most realisitc racer' and GT5 isn't 'the real driving simulator', so those false claims really are a given for just about every console racer out there.
That doesn't mean it's perfectly fine or anything, all I'm trying to say is to get used to it. Games are like movies, in a way. You'll only see the best parts of it during previews and stuff...
Anyways, I would've bought Forza 4 on release day, either way. So unless they show me something that's totally driving me aways from the game, I'll be getting it...