I'll see it when I believe it. He's 36 years old with "experience" as a JJ black belt. He said he's committed to "training MMA" for the next 6-7 months.
A couple of scenarios I can foresee:
A) Gets injured in training and the hype will fade off into the sunset
B) Pull a batista (go 1-0 vs some scrub, disappear and go back to WWE)

C) Get his face turned into mashed potato by a no-name MMA amateur.
He doesn't have the natural athletism of Brock, nor any real competition experience.
I would have loved to see Kurt Angle try MMA back in his prime, he could have done some damage.