Ujm, there is at least one posek(who happened to be chasidishe) who held that messianic Lubavitchers are apikorsim; that’s Rav menasheh klein, as i mentioned above.
But I haven’t heard anyone else say that. Everyone else I’ve heard from just thinks they’re meshugoim.
But the messianism is nothing compared to the deification issue, and it’s only getting worse.