If I'm not mistaken Repubs will need 60 votes in the Senate to repeal it even with a Republican president
Once an entitlement is in place the Republicans treat it as sacred just as the Democrats do. Is Santorum or Romney promising to get rid of Medicare? So, no Obamacare will not be repealed. It will be a thorn in the side of the Republic forevermore.
Prohibition was not an entitlement program. Once people get "free money" from the government it is political death to take it away from them.