Safe to say he can/will, otherwise they wouldn't have booked this feud in the first place. Obviously not for the full normal Shellshock set up seeing as how he struggled with Tensai and Heyman, but I can see him having no problem performing it in a basic Fireman's Carry position. Seems to me like WWE want to create a WrestleMania moment for Ryback.
Disclaimer: Obviously, the most likely choice for WWE is that Ryback will win at WrestleMania, as he is an upcoming and rapidly rising star, where's Henry is near retirement. However, it wouldn't surprise me the least if Ryback lost, so they can continue this feud.
Oh BTW, Ryback lifted Tensai on countless occasions during their match. Only problem is, that the Shellshock is such a difficult and awkward move to do, especially on a heavy opponent the size of Mark Henry.
If Ryback is going to use an alternative finisher he has to win with it before mania and build it up. If not, what kind of match between monsters would it be if the winner doesn't even use his finisher?