It's difficult to predict the future because things can change quickly in the shl or any other sim league really, but I think teams that are likely to be good one year from now are Texas, Edmonton, Toronto, Tampa Bay, Hamilton, Buffalo, Chicago, probably Atlanta and maybe Calgary.

Texas is already one of the best teams in their conference and they're a few seasons away from their peak.
Edmonton has been a playoff team for as long as I remember, they might not always be favorites to win but they always manage to have a good roster.
Toronto has a good young team and they're gonna be a threat to make the playoffs in the great lakes as soon as next season.
Tampa has enough prospects to field 2 teams, some of those prospects will build good players and by 2021 they will have a great roster that is 2-3 seasons away from its peak, like Texas / Toronto right now.
Hamilton, Buffalo, Chicago are the best teams in the league right now but cap space is gonna be a problem, so these teams should still be good but maybe not head and shoulders above the rest.
I'm not sure about Atlanta, their core players are in regression and they might not have enough prospects ready to step up, due to being an expansion team. Similar thing with Calgary and Manhattan who are no doubt playoff teams at the moment but don't have much in terms of prospects (though I haven't looked at the budgets, maybe I'm wrong)