Even tho Apple just refreshed the 27” Would it be “normal Apple” to update both models at the same time using Apple silicon?
It is hard to say what is "normal", as these transitions only happened once before for the iMac.
Last time with the switch to Intel the time line went like this:
June 2005 - Apple announced switch to intel in 2006
Oct 2005 - Last iMac G5 was launched
Jan 2006 - First Intel iMac was Launched
This time:
June 2020 - Apple announced switch to AS
Aug 2020 - Maybe last Intel iMac launched
??? ???? - First AS iMac launch
People can say that it might be a while, but who thought that Apple was going to release an Intel iMac just a few months after the last G5 iMac was launched.
Of course, this is a totally unique situation and you cannot always go by historical data to make predictions like this.
Basically, no one on the MR forum knows for sure. No one has inside info. We are all guessing. The next iMac might come out next month or 3 years from now.
The best advice I can give is that if you need an iMac now, or if you have compatibility concerns about the AS Macs, I would just get a Mac now. If you can wait and you have no concerns about compatibility, just wait.