Isn't the floor 28M?
A few of us that follow the numbers closely have done the math and Washington shouldn't have trouble reaching the minimum; along with the salaries, some of the players are on entry level deals (Ovechkin and we expect Green on the roster; Fleischmann?; even Backstrom if he comes over) and will earn some performance bonuses that will factor in the cap calculations.
Counting the 18 players signed (11 including Mike Green getting promoted from Hershey and Pothier's new deal) or qualified (7 from the end of season NHL roster) by the Capitals, the Caps are at approx. 24 million; that figure includes maxing out Ovechkin's performance bonuses, but does not take into account possible performance bonuses for other entry level players or signing bonuses, which also count towards the cap.
Perhaps a player or two that were qualified will not accept their offers, but most should sign; also, there is a good chance some RFAs will receive a raise/multi-year deal above their qualifying offers (e.g., Shaone Morrisonn; Matt Pettinger).
I think the Caps will take advantage of another team's cap or RFA problems to add a player, but only if the right opportunity presents itself and, in theory, will benefit the Caps (e.g., the Friesen situation last year). McPhee has stated that he is still looking to add a d-man this off-season, possibly via trade, and a top 6 center could be another possibility if the right player was available.