I think somewhere down the line we may find out that the wraith are the result of the Ancients, either as a cure to the megaplague or a race they tried to mold into their image as they were ascending.
I think the timeline is going to look more like this:
1...Ancients expand outward from Earth
2...Ancients build Gate Network
3...Ancients expand to other galaxies
4...Megaplague
5...Ascension starts, Milky Way is re-booted, Wraith are created - all as fixes
6...Ascension continues, Wraith turn on Ancients (why ascended do not interfere)
7...Atlantis becomes last stronghold of the unascended (important term)
8...Atlantis is sunk, Unascended leave Peagus
9...Unascended fight Go'auld, Ascension continues
10..Stargate SG-1
This is A LOT of speculation.
