Trump won't be able to pull it off. Too many people think he's just doing it for the publicity/lulz, the birth certificate comments will rub some conservatives wrong (in a recent poll I think conservatives were split about 50/50 over that issue), his past doesn't make him a candidate for saint hood, he has little to no support seated in the house or the senate and it'll make him unable to get anything done.
There just really isn't a polarized GOP or independent candidate out there right now that is willing to make a go at it. Romney would get my vote but I don't think he'll be able to pull it off either. There are people out there that should run for the GOP ticket but won't because they don't want to inherit this shit sandwich and put their families through 4+ years of misery. The GOP is also going to have a hard time garnering the minority and female vote too...in the case of women, the democrats will go after the GOP for their purported war on women and the GOP dug themselves that particular grave for that battle already.
I think we're gonna be stuck with Obama for the next four years...the good news is, he can't a third term.