It seems likely at this point, but as other posters have stated, 18 months is a political eternity, and anything can happen.
The biggest obstacle for the Republicans at this point is the field of candidates. In order to have a chance at organizing a ground game and raising money to compete in the Iowa primary, candidates should already be in that state and officially in the race.
Candidates such as Newt Gingrich and Rick Santorum, and potential candidates Michelle Bachman and Sarah Palin are not serious electoral threats to someone as politically savvy and well spoken as the President.
Jon Huntsman of Utah could pose a challenge, but he will have to walk a fine, perhaps impossible, line between a base split between Tea Party activists, business Republicans and social conservatives. Embracing Medicare cuts as Paul Ryan has done seems necessary to survive a primary, but deadly for the general election.
Mitt Romney has money, experience, and strong ties to the business community, but is going to be damaged by starting a state health care plan in Massachusetts that is very similar to the national plan of the President. Tea Partiers will run against him on that platform, and it remains to be seen whether southern states will embrace a candidate of the Mormon faith.
Anything can happen, and political and economic fortunes can turn on a dime in this environment, but at the moment, it appears to be President Obama's to lose.