Trump is just pandering to the birther element in the Tea Party in an attempt to forge an alliance with them. This is similar to when he said he was pro-life at CPAC (when he has indeed in the past said he was pro-choice).
Trump has the money but he also has enough baggage to sink the Titanic. Countless wives, flip-flopping on issues, his spectacle with Rosie O'Donnell, and now the birther issue. The left-wing media will tear him apart if he decides to run: we will see countless clips of him calling Rosie names as well as clips of his birther comments. We will hear comments such as "do we really want a sexist birther in the White House?"
The birther issue is a gamble -- it might pay-off or it might backfire in a very big way.