You'll be fine, there will be http2 for the next couple of decades at least. By then you'll be saying "Siri set up nginx for reverse proxying my new email server and open-facebook federated instance, oh and turn on the coffee maker, i'm gonna grab another 15 minutes of sleepy time"
V3 still seems to be experimental in nginx: https://nginx.org/en/docs/http/ngx_http_v3_module.html