Nothing's gone forever
No One Lives Forever's rights disappeared last year. Activision said it didn't have them and, in short, no one seemed to have them.
Siliconera spotted trademarks for No One Lives Forever, The Operative, Contract J.A.C.K. and A Spy in H.A.R.M.’s Way, filed by Night Dive Studios. Night Dive republishes classic PC games like System Shock 2.
As Siliconera pointed out, these are trademark filings. A copyright would mean rights to the source work. But without already having those rights, it wouldn't make sense to file the trademark.
Night Dive CEO Stephen Kick responded to Siliconera with the following statement: "At this time we are unable to comment on future plans. I would like to add that our team has a great fondness for these games and our hope is that they will one day be re-released."
Play coy for now, but I'd like to not live forever, again, and this is the best indication that that may still happen.