It's difficult to tell. At this time in 2007, everyone claimed Rudy Giuliani was the inevitable nominee, and he left the race with one delegate a few months later. This race is even more fluid and unpredictable than that one, in my opinion.
So far we have had Romney, Bachmann, Perry, Cain and now Gingrich assume the role of frontrunner at one time or another, with the lead sometimes changing over the course of days.
As for the debate tonight, we saw different candidates coming after Romney or Gingrich, trying to knock some of the points lead off of them, but no one seemed to land direct blows. The more important result is that Gingrich emerged intact, and as of now seems to have the inside track.
All bets are off, however, until we at least see the results of the first few primaries. At this point, I would bet on Gingrich winning Iowa, but not decisively, Romney taking New Hampshire easily, and Gingrich winning South Carolina by a lot. After that, it will be Gingrich's to lose.