This comment from the BBC's correspondent is helpful (apologies if I am breaching copyright!): http://www.bbc.co.uk/news/world-africa-15854418
"In the light of Tuesday's announcement from the government that next week's parliamentary elections are going ahead, and that presidential elections will be brought forward to next summer, the situation around the protesters is a little more complex.
It's important to remember that the Muslim Brotherhood - which is probably the biggest opposition group in Egypt and certainly the best organised and the most influential - is not part of this protest. It wants the elections to go ahead, and lots of people in the square don't want elections. They say they would rather have the military government stand down first.
It's not February any more, when people were united in calling for the government to stand down. Different opposition groups have got different agendas now. Egypt is growing into an era where it has proper competitive party politics.
While Tahrir Square compels the eye, it's not representative of the whole of Egypt - probably not even the whole of Cairo."