I doubt we'll see Rayleigh involved in this war. He's a retired pirate...why would he care?
As I was saying in the last thread...I think Ace is going to die, and Luffy is going to retreat.
If it does come down to this, then the arc can be shorter than you'd think...and Luffy could go back to finding his crew afterward.

If whitebeard ambushes Impel Down and rescues Ace before the schichibukai and marines are able to mobilize, then maybe they can save Ace, but I can't see any way that Oda could conceivably eliminate the world government from the series and still maintain content for the second half of the storyline. Keep in mind that some of the world government backstory is deeply rooted into current mysteries as well as some of the individual character development.

Also....a successful Ace rescue kind of...contradicts the whole "Dawn of a new era" foreshadowing that's been looming for the past 3 arcs.