Each successive Stargate
series has attempted to one-up the last. First it was set in the Milky Way, then they went to the Pegasus Galaxy, and then the universe. The natural progression if you continued to follow that pattern would seem to be time travel or the exploration of other realities. But that's been done before both on the various Stargate
series and in other scifi franchises.
I think they should take the opposite tack and pull back to the have a more Earth/Milky Way-centric show again, still set in the same universe with no reboot or reimagining, and show the implications of revealing the Stargate Program to the world at large, and the fallout from that revelation. It's frankly something that should have happened in the first series (and did to a lesser extent with the IOA) and is inexcusable that it didn't happen throughout Atlantis
By returning to an Earth-based series, you can occasionally have follow-ups with the characters and settings from the three previous series to show us how things are going. Hell, even if you can't book someone from Universe
, just have them appear in the body of a human avatar using the stones. CGI sets have made remarkable strides if you can't afford to rebuild the standing sets from the series themselves for a brief appearance.
I'd be interested in seeing how all the medieval and Egyptian themed human planets have come along in the post-Goa'uld-era, and whether they have started to build relations with their human counterparts on Earth and other planets. I'd like to see some missed opportunities or mysteries addressed (like the Furlings) and the return of some classic villains now that Earth is much more powerful (see if the Aschen Homeworld survived for example).
Then you can have different factions on Earth vying for control of the Stargates and alien technology.
Basically bring the show back to its more down-to-Earth roots from SG-1
but use that to explore new perspectives on existing characters, aliens, and tech, while introducing new planets, people, and factions we've never seen before. It's stilla big galaxy out there, and there's no need to go further and further out to tell interesting stories.