Running 10 gTLDs is about as hard as running 1 TLD. You already have the nameservers and the servers that handle registering domains, etc. Most of the rest of the work is done by registrars.

Further, TLDs are bought and sold periodically. I haven't seen any gTLDs go away. Is that something you've seen?

Otherwise, the concerns listed seem like FUD with no evidence so far.