I say this as a huge fan of B5: I'm glad they told him to bugger off.
Thing is, as much as I like B5, I've never really been able to get along very well with pretty much anything else he's done since (that wasn't a close collaboration.) Part of that is on me since I find his authorial voice so recognisable, it often takes me right out of the story. It's weirdly off-putting for example to be reading a Superman comic, and suddenly (figuratively) hear Clark speaking in G'Kar's voice. Hell, a few weeks back I was watching some old RGB episodes on youtube for the nostalgias and it just so happened to be one of his, and sure enough, about 5 mins in, Egon starts cracking wise like Garibaldi. I mean that's some serious character cognitive dissonance! At least Superman and G'Kar are in the same philosophical ballpark...
So yeah, as much as I think DW needs a fresh creative in charge, I don't think this would be a good fit. they might invite him to write an episode, but for various reasons I doubt anything will come of it.