Ron Johnson didn't vote with Cruz, but with Dingy.
I think he can be co-opted. He’s pretty solid on a lot of issues (actually tested, unlike Johnson).
Going to this meeting (when he could just as easily not have) may be a sign that he sees which way the wind is blowing.
Levin had him on last Thursday give it a listen to see how much of a worm Johnson is. He sounded like a democratic talking point specialist.