Best possible scenario (which is also probably the least likely scenario): Egypt emerges with a populist democracy, modeled in legitimacy of the likes of the populist democracies that spread across Latin America in the past decade (though not necessarily modeled in ideology). This would be truly representative, with a focus on helping the poor and disadvantaged. It is the least likely scenario because America and Israel (along with the other Arab dictatorships in the region) will do everything they can to prevent this from taking place. Historically and presently, America despises populist democracies, and if they cannot manipulate election processes or install U.S.-subservient "democracies" then they will resort to destabilization, coups or war. (A good recent example is Haiti, where the people have been collectively punished by America, Canada, France and the West for electing a popular democratic leader, Jean Bertrane Aristide, which was simply unacceptable to Western interests, so he was subjected to two separate coups and destabilization campaigns).
A more likely scenario is that Egypt is left with a transition into a neoliberal democratic state, in which all the candidates and parties are pre-approved by the U.S., heavily funded by Western NGOs and "democracy promotion" organizations (like the NED, NDI, IRI, USAID, etc). This was done throughout Africa and Latin America in the 1980s and 1990s, as the backlash against dictatorships spread through those regions. The dictatorships of the neoliberal era were Western puppets who were responsible for imposing the brutal "structural adjustment" policies demanded by the IMF and World Bank which amounted to 'social genocide' and extravagant foreign debts, enslaving the people to foreign creditors while enriching a national tiny elite who were subservient to Western interests. Thus, the neoliberal policies were viewed as illegitimate, since they were demanded by foreign powers and imposed by domestic tyrants. Hence, in the late 1980s and early 90s, a new strategy aimed at "democratization" was shaped, in which Western (particularly American) NGOs and "democracy promotion" organizations would fill the gap left by the social destruction of the neoliberal era, and would support neoliberal democracies, with a focus on elections, multi-party systems, "independent" media, and building a civil society, all of which were funded by Western organizations and governments, to ensure that the resulting civil society, parties and politicians were subservient to Western interests. Thus, more legitimacy was granted to the neoliberal program, as it was "democracies" which were now imposing "structural adjustment", and the people had "choice" in elections, where they could 'choose' between two or more rival factions of elites (all of which were subservient to the same foreign interests). This is the American model of democracy, such as having the Democrats and Republicans be presented as "different", allowing the people "choice" in who fucks them over for the same dominant economic interests.
The "Islamic threat" is largely concocted to scare white people, westerners and others to ensure that if an Islamic populist movement emerges, it could be crushed and destroyed, and everyone would view it as a "triumph" for freedom and democracy.
There are also a number of other plausible scenarios, such as a military occupation or war, but let's hope that never comes to pass.
America is attempting to mitigate "transition" or "unity governments" so that it can manage the process of change. This was done in Tunisia, and now it is being done in Egypt, and in both cases, American contact and influence over the respective militaries has been pivotal to this process.
If one thing is true of all revolutions, it's that the real struggle begins once the regime has fallen. However, Egypt's regime hasn't even fallen. Mubarak is gone (thank god), but that's just the first step. If the revolution does not confront and challenge American and international dominance over their nation (and military), then it will become a still-born revolution.
I hope Egyptians find a voice in a populist democracy, but Egypt is so strategically important to American, Israeli, and Western interests that it seems unlikely, and I think war or domestic military oppression would be more likely.
But perhaps there will be a Western-imposed democracy, in which case there could potentially be another backlash years down the line, as its legitimacy is destroyed, just as occurred in Latin America against the Western-imposed "democracies" that emerged in the 80s and 90s, which experienced their backlash with the populist democratic wave spreading across Venezuela, Bolivia, Argentina, etc. But again we see that America does not like populist and representative democracies, with the attempted coup in Venezuela in 2002, and the more recent successful coup in Honduras in 2009, where a subsequent U.S.-supported dictatorship has suppressed and crushed and even killed many opposition leaders, unions and other democracy advocates.
Empire is a very dangerous game, and unless the protests and revolutions spread and become more anti-imperial as opposed to simply anti-dictatorial, I fear they will be ultimately "managed" through the change. Just like Hilary Clinton said, the US wants an "orderly transition", which in diplomatic speak, means "managed transition", not true inspiring revolution.
I am happy that the Egyptians managed to get rid of Mubarak, and they have the blood and scars to prove it, but now the real struggle begins.