Welcome back, Victor! You were missed.
The folks doing business now as OtherSide Entertainment (as in, "what's on the other side of the looking glass?") have said that, having gotten the band back together, they want to be making games for years to come.
If Underworld Ascendant does well enough, I would be very surprised if a game in the System Shock or Thief molds wasn't next in line.
And the fact that someone was finally able to get System Shock 2 on GOG by negotiating successfully with both rights-holders gives me a tiny kernel of hope that OtherSide might even be able to call it System Shock 3.
That would be something.
In the meantime, the OtherSide forums are buzzing with ideas for Underworld Ascendant. Not all of them are contradictory, even.