I see no reason to say "hey, we have cap space to waste" and then waste it.
Realistically, we're looking at having one top nine spot open, and if we draft Stenberg, that's where he's going.
Yes, Sherwood, Toffoli, Goodrow, and Gaudette should be pushed down or benched, but realistically, this isn't going to happen, and players like Marchment or Mantha aren't really any better than Toffoli or maybe even Sherwood, and are going to want (and get) term.
No, I do not buy that Mantha is a legitimate 30 goal, 60 point forward; he's 32 and has seen his shooting percentage almost double over the last three years; that's a big sample but he's 32 and often injured, he's going to be just a second Toffoli making $7-8 million over 3-4 years, and he's likely to decline like Toffoli too. I'll pass. Marchment just isn't that good and is going to cost the same for the same term.
We're likely not getting these guys for a one year, even two year deal, so we're just burning cap space, and they're not realistically meaningful upgrades - hooray, we've moved Sherwood down to the fourth line where he belongs, but now we have three Toffoli-quality wingers eating up playing time, not being easily movable because nobody wants a $7 million boat anchor, and generally just holding our actually-talented young forwards back.
A young, quality forward? Sure. A fourth liner better than Goodrow and not too expensive? Sure. We don't need to spend money just for the sake of spending money and only marginally improving the team, if at all, because we happen to have cap space for now (and that's cap space that is rapidly going to disappear as our young players get extensions).