Oh no doubt. In my opinion Sharp and Seabrook will both be gone, but I can take solace that we made the most of this stacked core, though one more cup would be nice :P
Plus like you said Saad, Toews, and Kane aren't going anywhere and 22, 27, and 26 respectively. We have good talent in the pipeline, such as 20 year old Tuevo who's playing on that aforementioned 3rd line already in serious playoff games. The blue line depth is a concern, especially when Seabrook leaves, but Dunc doesn't show any signs of slowing down even at 31, plus Hjalmarsson won't be going anywhere and he's only 27, plus the brief time we saw 23 year TVR he looked good, but we will need a cheap blue liner to figure it out and become really good for a few seasons to be the cup favorite every year like we've been for the past 3 years (again in my opinion).
We should always at least be in the playoffs every year with our core, provided we have someone in the pipes who can hold his own, which always gives you a shot.