I stopped patronizing GoG awhile back due to their half assed porting of some DOS games that weren't available on Steam (still isn't a good Interstate 76 port sold anywhere, and it still plays not that great in DOSbox. I would literally have to fire up a Win 98 SE machine to play this game right to this day) and their lackluster Linux 'support'.
doubt they will remove it, it's intertwined with all their games and iirc still works this way in 3. they _might_ do it long after 3 to get some more sales and when they don't want to pay for the server anymore.
dunno why they did listed it in the first place, hitman 2016 is probably the worst game in that regard, even NMS can work offline just the same (although I dunno how the new stuff like expedition works, although it shouldn't be much of a problem to do it on you "local" version).