I currently have an Nvidia GTX 1080 with 8GB of GPU memory. It can interpolate 720p but not 1080p videos.

Will the Nvidia RTX 3080 be able to handle 1080p interpolation? The RTX 3080 only has 2GB more GPU memory for 10GB total.

Hard to tell since, as my thread already mentioned, DAIN doesn't work with RTX 3080 at the moment.

Some guys  tested it with other GPUs    and they say: 1080p needs 10 GB Vram  with  "half precision" enabled

But you can't be sure if it works or not.  Perhaps in some cases  it will   exceed 10 GB and so you have no buffer. But in some days there will be benchs with the new GPUs.

Wait for the 3080ti, which is rumoured to have 20GB of vram. I mean not that you'll be able to get one until way into next year, by which time DAIN may support the 3000 series.

Today  Dain-App 0.48 is there (later for the public)  it should work with 30x0 cards

https://www.patreon.com/DAINAPP