I think the Shovel Knight game looks really good, and I plan on getting the physical release on Wii U when it releases. But I don't think he should be in Smash at all (if by hook or crook this turns out to actually be true). I enjoyed Shantae a lot too, but I don't think she should be in Smash either.
We have a standard of proven and legendary 3rd Party characters so far. They have all stood the test of time, for decades. They all have a huge legacy, and they all have significant ties to Nintendo, be it through support, or rivalry.
Even if Nintendo wanted to go the Indie route for a 3rd Party, then Yooka-Laylee would be the best characters. OK bias aside, Shantae would honestly be the best choice. At the very least she has multiple games, and she at least has a long history (with Nintendo). She is also guaranteed to stay around for a while. Shovel Knight may NEVER even get another game.
The word 'deserving' is thrown around a lot. But Shovel Knight is truly, truly undeserving of being in Smash Bros.