I'm not super familiar with how HW acceleration is implemented in practice, but I imagine that a lot of the "building blocks" for HW accelerated AV1 will be reusable for AV1.1. If that's the case, as long as a mobile device gets the right software updates the hardware for AV1 will still be beneficial for AV1.1.

If I'm parsing what I read right: 1.1 prohibits some narrow tiles--not the little 4x4 transform/prediction tiles, larger independently decompressible tiles that are used to allow parallelism. I suspect nobody was generating the narrow tiles before: it would be bad for compression, since the whole idea of these tiles is you can't predict across their boundaries. But they were technically allowed even if they didn't make sense.

The other things I see are a new option that doesn't break existing AV1 streams, and a couple changes that look like essentially editorial cleanups that were deferred during the spec freeze to avoid confusion.

They were right not to do these changes during spec freeze, but (at least from what I can see) they're not practical issues for folks considering AV1 encoding today.

Hardware will support both AV1 and AV1.1 too.

Don't delete the source gif and reencode when needed? Is there some situation in which AV1.1 > GIF > AV1 such that it would be worse to use AV1 today but better to use AV1.1 later?