Hardware-wise, the Apple-Silicon Macs will have better performance and battery life than their Intel-based counterpart out of the gate. I mean - if they don't, why release them and expect people to buy them?
But the key to realizing all that performance is to have software native to the platform. All Apple software will be native at launch and run very well. Additionally, iPhone and iPad apps should run fine. (Touchscreens anyone?)
So, if you rely mostly on Apple software and iPhone/iPad apps, it's probably safe to get an Apple Silicon Mac at launch.
But if you also use some software on the Mac that doesn't come from Apple, you're relying on how rapidly developers port their apps over to Apple Silicon. Rosetta 2 will allow you to run those apps in the meantime but note that you'll take a performance hit (how much - TBD) and you might not see any benefit over the same app running on Intel (where it is native.)
If you rely upon or use a lot of these third-party apps, you may want to hold on to what you have, or buy the last, best Intel-based Mac, and jump over to Apple Silicon when you see your favorite apps ported over. If you use only a few of these apps and/or Rosetta emulation performance is acceptable, then Apple Silicon could still be acceptable.
But, if you use or rely upon non-Mac software (Windows under Bootcamp or Parallels/VMWare, etc, or Linux), you know the answer - you have your machine or buy an Intel-based Mac now. (Don't expect or anticipate Microsoft to port Windows over, because you will also have to see if Windows developers port their software over to ARM Windows as well, as emulation performance will stink.)
In short - make your decision on your software needs, not hardware.