The big issue with NVidia GPUs is that NVidia won't allow opensource drivers to set the clock rate on newer graphics cards.
However even on older cards where this is not an issue, community drivers tend to lag behind. It is far for a breeze. So far they are leveraging the Mesa driver infrastructure to implement OpenGL ES 2.0, which is a good beginning. The really hard part is supporting all of the latest technologies at a good performance. It's too early to know if that will be a breeze or not.
So this sound like the people who say we will be able to run first real tests by 2024 are likely right. From there it's then "only" as much work as with Nvidia.
So maybe by 2032 we will have some M1s with somehow HW accelerated graphics. At least it looks like that given the history of Nouveau.
I don't want to put the work down those people are doing! But the truth is likely that without vendor support this will never fly beyond some tech demos.
I'm not sure I'd be so pessimistic either. Perhaps they'd be able to use the open source AMDGPU drivers as inspiration, or perhaps there is something else I'm not thinking about. I think there's a solid chance they get it usable for basic use within a few years.
However even on older cards where this is not an issue, community drivers tend to lag behind. It is far for a breeze. So far they are leveraging the Mesa driver infrastructure to implement OpenGL ES 2.0, which is a good beginning. The really hard part is supporting all of the latest technologies at a good performance. It's too early to know if that will be a breeze or not.