Hellebuyck should be a keeper; It is pretty much just him and Vask. as the top tier in goalies, so hold onto him.
Barkov is young and starting to come into his own this year, I would say he should be a lock going forward also.
It also could be because I'm a J.Hughes owner as well, but I would consider him a keeper going forward as well due to his huge upside/potential.
I should also point out that you could likely be losing Kaprizov's minor eligibility. If you can keep him AND J.Hughes apart of the minor system, that would be huge, but I would almost consider Kaprizov a keeper going forward based on what we are seeing from him this season. He could be just as productive as J.Hughes for the next few years (but maybe not as much upside longterm).
P.Kane and Ovechkin are still top tier right now, but the longer you hold them for, the less return you'll get in years to come. You could always try to flip them for a younger skater who maybe isn't there yet, but could be... maybe Pettersson, Boeser, Aho, Rantanen, or Point? But you have to ask yourself if you are willing to hurt yourself this season when you are in the position to win it if you make the trade before it ends. If you can wait to move them in the offseason, that would be ideal.
Zibanejad, Hamilton and Carlson is where it gets tricky. Zib is having a huge off year, and could rebound, but unsure. Hamilton is doing alright, but his peripherals aren't quite there in a league that promotes hits and blocks. Carlson is also starting to get up there in age as well.
I am unsure of your other owners in your league, but I personally would look at moving Wheeler, Zib, Hamilton, Carlson, Ekblad in some kind of a 2/3 for 1 type of trade, to get a player like I listed above. If you can't keep Kaprizov on minors, then that makes it difficult;
Ideal world; here's what I'd try to do; (I'd also be trying to insure I win this season too and make these moves in the off season)
Hellebuyck, Svechnikov, B.Tkachuk, Barkov, J.Hughes, Kaprizov, and then move P.Kane, Ovechkin, Wheeler, Carlson, Ekblad, Hamilton in some kind of a 2/3 for 1 and try to get an Eichel, Marner, Pastrnak. Find the owner with the weakest 8 keepers, and leverage that.