The change will likely be more qualitative than quantitative: the Democrats clearly do not have the votes to override a Bush veto.
But Bush can't fund his own war. If he vetos the bill, he doesn't get his emergency funds. He's gambling that the Democrats will cave in in the end, that they won't allow the surge to go unfunded.
But time is against him. This war is getting more unpopular, the Democrats haven't suffered for their votes, polls suggest that nearly 60% of the public support leaving Iraq in the next year. Republicans are getting tired of the scandals and many want the war done before it costs them another election.
And the Pentagon says it needs the funds in weeks or the surge is over.
This was never supposed to get through the Senate. Republicans were widely expected to filibuster any timelines in the Senate bill. The fact that they could come up with 48 votes against the language, but didn't attempt to block it, is a red flag that they're preparing to bail out on this.