How much data do you actually need? Enviromental-data do nomally not need live-updating. They do not change that fast ( exept rain when it realy poors )
Eventually you need caching if you want to be able to recall the last value instead.
Nope - and if The Things Network goes bankrupt, you can be sure there will come a fork, to make a new community driven network.
And as everyting is open source, you can make your own installation if it becomes a problem.
TTN will not be able to switch into a a paid service, as they do NOT own the gateways. That will properbly result in many (if not most) gateways switch to other networks, resulting in TTN not being workable.
So no. I don’t see any possiblity of that happening.
PS: Sorry for my english, but I cann’t write in german