If they bomb Mass Effect 3, I'll definitely look at future games they make with a skeptical eye. I wouldn't cut myself off from buying a new BioWare game forever, though. That would be silly. If they make a bad game, they make a bad game and of course, I'll be disappointed if Mass Effect 3 does not turn out to be as good as I hope it will.
But I'm not going to descend in a apoplectic rage and swear to never EVER buy a BioWare game again! I won't be devastatingly crushed with a feeling of bitter, heart-wrenching betrayal. They're a video game developer, not my closet friend, and if they make a bad game that isn't on par with being betrayed or abandoned by a loved one.
Will I "forgive" them? Sure, if they make another good game. I don't expect, or demand, every single game from a developer to be good in order for me to like them. I haven't liked every single game Valve has put out (I did not like the first Left 4 Dead for instance), but I still like Valve as a developer. I haven't enjoyed every single Call of Duty game I've ever played, but I have enjoyed some.
If Mass Effect 3 turns out to be bad or rushed, I'll be disappointed. A bit sad, even. But my life does not revolve around the games they make and after a hour of depressed moaning about how things "could have been" for ME3, I'll move on with life. I've played many a disappointing game in my life. I have not be psychologically scarred by them.