I'd definitely say it's worth picking up, especially since it's basically half price through Amazon, too. More like Code Name: S.T.E.A.L. amirite?
Honestly the thing everyone points to is the sales, but honestly...when has that really mattered? I admit it could be a case for, say, Henry Fleming not being DLC, since DLC needs to be bought separate, but for another game down the line? Not a problem at all.
For the record, Captain Toad is probably the only other Mario character barring
maybe Waluigi (where does Sakurai stand on the whole Mario vs Wario character thing again? I vaguely remember Waluigi being listed in Wario's series in the April Direct) I can see being added down the line, so I think he's a good bet for next Smash at least, whenever that may be.