Apple is still pushing it, which is great. I'm just not sure how well it's going to scale -- MPTCP adds an extra layer of indirection, and extra locking in the easy case where it's just one server handling an IP. In the load balancing case, people are going to have to teach their load balancers a lot of new tricks to get the subflows aligned. If using anycast, the client is likely to be using multiple networks, so using the same server address seems likely to get to a different pop; exposing a pop specific extra server ip seems like something people don't want to do, since exposing that may make it easier to do a single pop.

I've been debugging an issue where incidentally I'm hitting 1gbps on a single tcp connection (server to server, with tls), so I'm not sure why MPTCP is required? ;) But I guess if we had it, I would probably hit 2gbps instead of being capped by the one nic.