If the MM race write-ups are going to be included from the get-go, I think it would be a good idea make a note to the effect of, "these races are subject to change when new, specifically player-oriented write-ups are done by WotC, whether in Dragon or a hardcover book."
That way, when such write-ups are done, people can't gripe about getting nerfed or whatnot - they've been warned. If you don't have DDI and won't have the info needed to play the race if it gets done in Dragon, then you should either avoid them or get a 1 month subscription when that Dragon issue comes out. And if you don't want to deal with that issue when it comes up, then don't play a monstrous race that only appears in the MM/MM2. I don't think that's unreasonable, given the amount of headache it can prevent down the road.
I'm just recalling the little mess that was the proposal for the Dragon version of the minotaur in L4W, and I think LEB should learn from that and do what it can to avoid such things in the future. Just removing oversized from bugbears won't cover it - as stonegod mentioned, Shifty for kobolds is probably going to get changed (if not removed outright) when kobolds are done. Any of the other races have the potential to be changed drastically as well, and I think preparations should be made for if/when that happens.
In my opinion, warning players of monstrous characters that they will have to change their race mechanics if/when the race is done in more detail in Dragon/PHBX/a setting book/whatever is something that should be done.