It just feels wrong to buy anything new from Apple with "Intel Inside" - when they're clearly going to dump it soon, in favor of ARM (excuse me for not using the cringey term Apple Silicon).
Why does it matter? There will be a period where the Intel Macs are still supported and probably more stable, and it could be ~2y before your upgrade is available if it's ARM based. If you have a retina macbook pro from 2014~ it definitely makes sense to upgrade to a macbook pro 16" today. The thing will see you through another 5-6y easy.
However, I am assuming since the Macbooks are rumored to get ARM as early as late this year, it is likely iMac would follow next year too. The Developer Transition Kit has a Mac Mini with ARM already.