Depends on your keeper rules (dynasty or keeper?) and whether you are in contention this year. He has not been called up yet, and will not be called up until at least June 22 (the day after the Royals are done with playing in NL parks) in my opinion. It may be August for all we know.
If you are in contention, I wait. If you are out of contention, does he ever lose Waivers and become a Free Agent? I would pounce the moment that happens. Really, yahoo has him as a Catcher? He hasn't played catcher since 2010. He is likely to lose that eligibility next year.
Help with mine:viewtopic.php?t=448606