QUIC is already getting those optimisations as the existing large deployments are incentivised to do so, as one example Kazuho Oku from Fastly made changes to their TLS implementation that showed improvements to AEAD and header encryption[1]. I suspect we will see improvements to QUIC's performance at a pace faster than the optimisations to TLS were made to make ubiquitous use of it trivial.
[1]: https://mailarchive.ietf.org/arch/msg/quic/OnBhC4gCosmlU3VKo...