I tend to buy secondhand anyway, and yes, almost certainly it's best to wait.

At the moment, speccing out a local box more powerful than the machine I am using is largely an intellectual exercise, but it does have some value for understanding what a client might be able to use if they absolutely require on-premises inference, and I do have a couple who fall into that zone. So I am trying to keep up to date in principle, but the built machines don't get beyond the shopping cart.

The M5 Ultra has probably smoothed out the major issues of AI on Apple Silicon (prefill doesn't suck anymore) but the way Apple marketed that chip strongly suggests they are now fully aware of the strengths but also the limitations of their architecture and will get a lot more done.

It's properly put the (fairly equivalently priced) DGX Spark in the shade, though.