Heck no. I think Apple Silicon will be a huge benefit for MacBooks because it should use a lot less power and should be great for battery life. But I'm not expecting Apple Silicon to beat Intel in performance right out of the gate, especially Intel's desktop CPUs in the iMac. At best, I think Apple Silicon will come close to Intel performance while offering much better battery life for the first couple years, and maybe 3-5 years from now Apple Silicon will take the performance crown as well. But for an iMac, which is plugged into a wall anyways, power efficiency isn't of much benefit, and you will likely be losing the ability to run Bootcamp Windows, plus most macOS apps will probably take a decent performance hit until they're updated to be fully optimized for Apple Silicon. For an iMac, I would buy now and wait 5 years for things to shake out with Apple Silicon. For a MacBook, maybe I would wait for Apple Silicon.