You realize that HTTP/2 is still nowhere near to being adopted by corporations? It's really far fetched to plan HTTP/3 and expect any adoption.
Increasingly "corporations" out-source this problem to specialists who are only too pleased to use newer technologies with better performance and collect the same money.
The application servers running the site do not accept HTTP/2 and most likely can't support it at all (we're a python shop and none of the web frameworks we use could do HTTP/2 when we looked into it).
But for companies like CloudFlare or Googl HTTP/2 means less traffic overhead (multiplexing+header compression) and can save them a lot of bandwidth (aka. money) with that.
More availability of HTTP version gateways in load balancers and other reverse proxies is all that's needed, and that's coming along.