According to [link|http://www.pbs.org/weta/crossroads/about/show_jihad.html|Jihad], bin Laden and cohorts (in their own words) have wanted to start a regional war from China to Egypt and beyond in preparation for restoration of the Caliphate. It's hard not to view the events in Lebanon, Gaza, Iraq, Afghanistan, Sudan, etc., etc., as fitting into this plan. I don't know a lot about the ideology behind Hamas, but they certainly seem much closer to the Muslim Brotherhood and similar groups than to secular nationalist groups.
It's very hard for me to imagine Egypt considering rolling into Gaza without thinking about the consequences for feeding further internal unrest. Since Egypt has been part of the "near enemy" since Nasser's days, I'm sure Osama and Ayman would like nothing better than another pretext to incite attacks against Egypt. Seeing that, I don't think Egypt's government would have any interest in going into Gaza.
I suspect that most outsiders will keep a hands-off approach to Gaza until they feel they have no other choice. At that point, all bets are off. :-( I expect that Gaza will be fairly quiet soon (Hamas will want to consolidate their gains; Fatah will be too weak to respond), but the masses of people there will continue to suffer (partly because the West will have even more reason to refuse to support them). I expect the West Bank will be fairly quiet too, and Fatah will feel great pressure to prove to the population that it can govern (while cracking down on Hamas there).
Just my $0.02.
Cheers,
Scott.