SG1 has been cancelled after a record breaking run, the 10th season will be the last. SGA is to continue. SG1 will be missed, it's a series with rich mythology, delving into all sorts of ancient history although it is time to pass the baton fully. The franchise is a good one, no reason why it should not be possible to continue it in some form or another, even beyond Atlantis.
I'm expecting strong links between season 3 of SGA and season 10 of SG1 given where things were left at the end of season 2 of Atlantis.
Areas I'd like to see covered at some point in the stargate franchise include:
- Some history, i.e. the formation of the gate network
- The rise of the Goa'uld
- The Asgard - they're reasonably familiar, but it'd be good to see them from their own viewpoint
- The Furlings
- In SGA the Major Ford storyline needs resolving
With SG1 finishing, the difficulty of travel between Earth and Atlantis can be eased a little (to allow some crossover of characters), however, with the Daedalus giving a three week traveltime, this is not really a major issue anymore, so I don't think that they'll find a shortcut anytime soon (short of the demands of plot).
My main concern with SGA is that as things go on, the stargate universe is not 'left hanging' by the TV execs not giving enough notice of the money running out. It looks like SG1 will have a satisfactory finale, I hope that Atlantis will be treated well too.