For the server, maybe. But adding more players wont tax the individual client anymore than being on a server alone. I think if its well coded, it wouldn’t be very bad at all. If anything, the worst taxing would be the Karma system keeping track of who did what and who to punish or reward. Beyond that, basic things dont seem too bad.
If there can be 50+ player Gmod servers running TTT with low ping little lag, then Unturned 4.0 should be able to do it too.
Speaking of expectations, if Halo 3 can have Replays, then 4.0 should be able, too.
Shameless idea advert. It would go very cool with TTT, Arena, Survival, really the whole game.
EDIT: And if the karma system is too hard to code or too taxing, we could either keep it very simple or just not have it at all.