You wouldn't save much going from h.265 -> AV1 but h.264 -> AV1 should be a significant savings.

AV1 is ~30% more efficient than h.265. And h.265 is ~40% more efficient than h.264. The lower the resolution of the video, the less savings you will get.

I personally will wait until more devices support hardware AV1 decoding. I believe only Intel 12th gen, and Nvidia 3000 support AV1 currently. I don't plan on purchasing a new laptop or smartphone for 3-4 years, at that point I may start encoding in AV1.