Its looking like HTTP/3 will be all encrypted and all UDP, all the time
I started my web-ish life with HTTP 0/9. It was the dialect that 'escaped' from Cern. Soon after HTTP/1.0 came along, and then 1.1. And we stuck on 1.1 for a long time (more than 2 decades). And then HTTP/2 came along, and it was great. 100% encrypted, asynchronous, etc.
In parallel some folks started experimenting with HTTP and TLS-like encryption over UDP. This allowed them to build their own congestion-control algorithms independent of the operating system, to reduce latency of setup, of throughput. And it went quite well but was a bit controversial for some.
And now, after some discussion it looks like the camps are merging. There seems to be a fair bit of support for HTTP/3 to be UDP-based, all-encrypted all the time.
So, if you are still on HTTP/1.1, get going. HTTP/2/SPDY/QUIC/... are all about higher performance, better safety, more security, more privacy. Who doesn't want that?