For context RSocket was started by Ben Christensen (RXJava fame) and implemented by the Edge team not Tim’s team. All the original engineers still work on RSocket either at Facebook or my company. It is still running in production on Chromecast and Akira UIs at Netflix with the original RSocket implementation. I can’t speak to future plans.
gRPC vs RSocket is not the best comparison. It is better to think about RSocket vs HTTP/2. gRPC would easily work over RSocket. In fact it would be cool to have gRPC over RSocket. Then you could switch transports very easily. This would let you do cool things like gRPC over RSocket/Aeron (Aeron tests showed double throughput with lower latency than TCP) or you could use gRPC in a browser via websockets.
We have several ex-Netflixer at Netifi that have used both RSocket and gRPC and they are happy to answer questions.