We got one of the ‘Transition Kit’ Mac Minis, and we are working on updating VDMX to run natively on both Intel and ARM machines as a universal binary. We’ll give some further updates with an expected ETA for this release once we get deeper into it.
Apple has said that the existing Intel machines will be supported at least for the next few years, and there are even some new releases with those chipsets still in the pipeline, so I think it is a safe bet to buy a new Mac now.
Beyond that, if you want my pure speculation, my guess is that Apple will start by replacing the lower power machines such as the Mini and the Macbook Air in their lineup like they did back in the PPC -> Intel switch. Another thought is that these last generations of Intel machines may have very high resell values down the road (if you keep them in good condition!) as there will eventually be a lot of demand for this hardware to run software that doesn’t make the jump to ARM.