It could still be Romney, but not necessarily. Other angles to consider:
1) Gingrich could gain more traction by claiming he has experience standing up to the Clintons before
2) Someone who stayed out of the race in our timeline (like Christie, Huckabee, Trump or Palin) might actually make a go for the nomination and win it (Palin vs. Clinton would be historic but unlikely)
3) Clinton's hawkishness makes Republican voters react by being more open to isolationism and they nominate Ron Paul or Gary Johnson (again: unlikely but not impossible)
4) Some other establishment Republican (Jeb Bush, Tim Pawlenty, Jon Huntsman or somebody else) manages to seize the mantle of establishment candidate and gets the nomination.