Political Insider have done the maths on delegates, and found that, after the Pennsylvania win for Hillary Clinton, she is actually less likely to win the Democratic nomination than before it:
...before the Pennsylvania, Sen. Hillary Clinton needed to get at least 63% of the vote in the remaining states to have a chance to win more delegates than Sen. Barack Obama. Clinton now needs 296 of the remaining 435 delegates up for grabs (or approximately 68% of the vote.) In contrast, Obama needs 140 of the remaining 435 to have the majority (or about 32% of the vote.) Therefore, despite her win in the Keystone State, the results have in fact made it less likely Clinton can win.