I wonder how Bioware is going to get round The Bad Ending from ME2. (No, I'm not calling ME2's ending bad, but there was a specific version ending that was Bad. I wonder how they will resolve that.)
If you are talking about the one I think you are talking about, the worst possible ending then I would assume that one won't be imported. Wouldn't really make sense to import it TBH.
Not to mention that to have this ending you really have to work hard for it, I mean you kind have to make sure to make all the bad decision possible to have it.
In DAO if you had the "bad" ending you can't import your character so it's most definitely going to be the same for ME2.
Personally I am more worried about what they will do with the companions.
SPOILER SPOILER SPOILER SPOILER SPOILER
Most of your companions can die even with the good ending, so I am a little worried that some ME2 companions end up being relegated to useless NPC like the "killable" ME1 characters were in ME2.