I think Brock will be around for a while.
He said the reason he left, the first time, was because "The devil was always knocking on his door."
Things are different, now. It's not a bunch of guys in a car. The top guys travel rockstar style in their own tour buses.
Plus, when his WWE contract ends, he'll be 37. That's prime for a pro wrestler but old for an MMA fighter, especially one coming off a long layoff and who didn't have top tier MMA skills to begin with. Moreover, I don't see a Hollywood career in his future.
IMO, WWE is his best bet.