I apologize if someone already mentioned this, but here's my prediction.
If McCain wins the Presidency, and the democrat gains in congress are not a route, the new AWB will never see the light of day. They could get it passed, but not with veto proof majority. McCain would veto. Thus, it will not get sent to McCain as a bill.
If McCain wins, and democrats route republicans in congressional races, the dems will pass a new AWB, McCain will veto, and the democrats will over ride the veto. We get a new AWB. It will be challenged in due time, but how long will that take? Long enough for there to be some new judges on the Supreme Court? McCain better try to nominate conservative justices. However, if the dems control the Senate, he won't get any conservative justices through Leaky Leahy and his band of merry makers. McCain will have to settle for moderates. They may decline to hear a case, rather than bump up against Heller.
If Obama wins, the new AWB will be presented to him within the first few weeks in office, and he will sign it. There will be challenges, but again, how long will it take to get those challenges to the USSC? Will Obama have appointed new liberal justices to the court? Will they ignore Heller and rule that the AWB is constitutional under a lower level of scrutiny? Will they refuse to take the case? These are all events that could take place and must be considered as we vote this fall. Not just for President but for Senators and House members. If you don't want to vote for McCain, at the very least, get to the polls and vote for your conservative candidates for the House and Senate. Also, vote for conservatives at the state and local levels. Notice i didn't say republicans. Some of them are not conservatives, but are liberals wearing stinking GOP badges! Rant over.