@realjohnboy,
I think it's a mistake to think Mubarak is going anywhere, any time soon.
His pledge to have the government step down simply means that scapegoats will take the fall.
He will likely announce a series of reforms designed to take the steam out of the protests, including a promise for near term elections.
If this works he will, once the fire has been tamped down, take the opportunity to round up the leaders of the protests, beef up security and back off promised reforms.
It does appear that the Muslim Brotherhood is sitting on the sidelines at the moment, but it is simply biding its time and watching to see which way this situation will tip.
It also appears that the current protests are being led by democratic reformers, but make no mistake, if they prove successful in toppling Mubarak's regime, the Muslim Brotherhood is not going to simply let them enjoy the fruits of their victory.