(Very) rough estimates and personal guesses for next year's cap, before any UFAs are retained: assuming the Red Wings resign both of their notable RFAs (Tatar and DeKeyser) at say $3-$4 million combined, Tootoo gets a compliance buyout, and you factor in the bonus penalty the Red Wings are virtually guaranteed to owe (roughly $2 million; could be more or less depending on injuries and roster moves over the rest of the year), we're looking at 10 forwards, 6 defenders, and 2 goalies (Mrazek as the backup) on the roster at a cap cost of roughly $54 to $55 million. That would give the team up to about $15-$16 million or so in space to spend on the balance of the lineup (likely 3 forwards, 1 defender, and possibly a goalie).

That should be enough to pick up 1 or 2 big(ish) contracts, depending on cost and other stuff like whether or not Alfredsson wants to play another year, etc.

I would personally love to pick up a first-pairing defenseman either through FA (if any are still around by the offseason) or trade; he doesn't have to be the elite of the elite, just somebody who can help Kronwall shoulder the load and help prevent the likes of Smith and Kindl from playing more minutes than they really deserve. Markov and Phaneuf strike me as potential targets among those who might be available; if Alex Edler has fallen enough out of favor in Vancouver I think trying to trade for him might be worth considering.

That said, I would also caution against the wisdom of trying to build a significant portion of your core through free agency. With the cap going up and the FA pool likely being unwhelming (again), the odds are that the few attractive targets will get a lot of attention and end up costing a lot more than they're truly worth. I'm not saying you shouldn't splurge once in a while if you're going after a truly elite player or you have a very specific and pressing need (man, Ryan Suter would be /really/ nice to have right now), but as a rule not-quite-top-tier players (2nd liners, top 4 but not necessarily top 2 defenders, etc.) acquired via free agency are going to be overpaid. Try to build too much of your primary support that way and it starts dragging you down.