For the cult part, on one hand probably yeah because cults prey on vulnerable people.
But also the religious/psuedoscience aspect(s) might prevent some people from being interested and without that it'd likely veer more towards being classified as a gang/criminal-org. So it probably won't be dramatic.

I would say it could be more like a tribe or something similar, but with communities eroded away as they are now I doubt that will work out on a meaningful scale. From the difficulty of being able to provide food and housing (and that's now, before things get really bad) to people who might not be able to "pull their weight" or just general distrust of people on top of other issues like location and transportation.

Any half-decent option will probably spring up organically from people who have some connection already. I'm sure there are plenty of people now who don't have much of anything tying them down but there is neither a destination nor a community or means to get to one. With no information/contact, nothing about that will probably change especially when you think about actual chances things will work out as desired.

Preventable deaths will likely be the more dramatic rise, especially related to heat and natural disasters.