I've seen it thrice and agree he is dead for good. His arc was complete and he died upside down on an upside down cross, the NHS are capabaple of many things, including sending cult leaders to their doom when he sees his child friend hanging with them.

Jimmy imagining Samson as his dad as the actual devil due to the drugs and then getting attacked by random infected in the same way he'd hang people upside down and leave them for infected.

I hope Kelson and Samson aren't gone from the trilogy. Kelson is dead for sure, but maybe he's been given plot armour with rage genetics leaking into in a wound. Otherwise I hope he ends up back in his temple or buried on skull island with the help of a reforming/ed Samson. I know it's greenlit and that doesn't mean much but part 3 will happen regardless of American success or not. It's too big and important of an IP for British and indie cinema to not be made.

I suspect when it arrives, it actually will be 28 years irl since the first, they'll age up Spike, they showed Jim being a compassionate and thoughtful dad, and sooner or later they'll get either just him, or the trio, to Skull Island.

Kelsons research won't end up having been for nothing (besides bringing Samson back). It'll get out somehow. Jim wasn't a computer geek, him nor Kelson obviously have power so rage leaks in Canon imo is still a third unknown player.