I think it's unlikely that entered into their decision. No matter what year they release there are going to be more great games. In 2012, for example they will be competing with Bioshock Infinite, etc.
Bioware didn't really "change" the date because they had never announced a specific date yet. Probably some of the negative fan feedback for DA2 made them extra concerned with giving this final installation of the ME franchise enough time to do a phenomenal job with it. Maybe they wanted to release it on the Wii Cafe or whatever, who knows.
aye, none the less them pushing it back is a good thing I don't expect sweeping changes really as they are using what powered ME2, hopefully they think things over and realize they don't have a frothing brain dead fan base, that their fans are there because the games are good, not because they are hyped.
anyway Booty's and several other posts have /thread, Bioware said Holidays 2011 they didnt give a definitive date to ME3's release, Bethesda did for Skyrim, whether or not that is more/less susceptible to being pushed back is no ones call, **** happens, like the fire at Bethesda during Oblivions developement they could very well move the date forward or back or whatever, we're no one to say how concrete it will or will not be.