[jsarno]

I actually think Bush is going to completely get out of politics. If I had to place a wager, I'd say he's burnt by all the negativity, and quite frankly doesn't give a crap what the republicans are doing. I think he wants to head back to his ranch and not be heard from for a LOOOONG time.
Not being best friends certainly helps, and I would also not be surprised if the "higher ups" in the republican party asked Bush not to show in order to create that separation. All in all, it's a smart move for the republicans for him NOT to show. There is no positive scenario for him showing up.