Can't find 4.5, but 3.5 Sonnet is apparently about 175 billion parameters. At 8-bit quantization that would fit on a box with 192 gigs of unified RAM.

The most RAM you can currently get in a MacBook is 128 gigs, I think, and that's a pricey machine, but it could run such a model at 4-bit or 5-bit quantization.

As time goes on it only gets cheaper, so yes this is possible.

The question is whether bigger and bigger models will keep getting better. What I'm seeing suggests we will see a plateau, so probably not forever. Eventually affordable endpoint hardware will catch up.