In FC: New Dawn there is Sam's Paladin which contains his iconic suit and his note about something likely a large scale attack has happened on US's soil. Back in Sam's mission in GR:Wildlands, at the end Grim mentioned about a "empty quiver" which should be a reference to a nuke that has gone missing. And then in FC5 US got nuked. I think that if the relation between FC and SC is cannon and not just easter egg, it's likely that the next SC game will have something to do with FC5's nuke and maybe he failed to stop the attack. However, I personally don't want this to happen. Sam deserves more just than this after all.
I just hope that Ubi doesnt pull the old "Ubisoft" move on SC and turn it into a typical open-world game filled with too much stuff that most people never complete (thats what i've gathered atleast...). A level based campaign is the way to go for a Splinter Cell title, and nothing will change my mind about that.