Seems unlikely. Not every AWS user is in every region. They would need to have a separate range of anycast IPs for every possible combination of regions (2^N possibilities) to prevent packets from going into a black hole. If they wanted to be able to serve a conservative number of hosts in every region (say 32768) that would require 15-bits of IP space per combination. If AWS expands to 10 regions, that means 25-bits of the IPv4 space. A /8 only gives you 24.
I guess an alternative might be to do some kind of NAT for unbound anycast addresses which forwards packets to an available region, but that is hugely complicated.
I'd be delighted if they offered it for even just two regions. Right now if you want your service to be highly available you either run your own routers in two collocation facilities and forward to AWS, or you don't use AWS.
I guess an alternative might be to do some kind of NAT for unbound anycast addresses which forwards packets to an available region, but that is hugely complicated.