Yeah, it's difficult to speculate the 'A/Si family' expanding in any other direction in the near term. It's interesting, if this was the intent, that they wanted it known just after WWDC.
In the talk Srouji talks about how the Watch SoC was done at one of the Isreali R&D centers. The Vision Pro has the R1 chip. You don't need much speculation to see there are 'cousins' of the M-series sequence. Or that there are more than just the plain M1 ( Pro , Max , Ultra ) . He also said get into the hands of 'millions and millions'. An "extreme" is not going to get into the hands of 'millions and millions' at all.
Apple has 'A' , 'M' , 'R' ,
and 'S' series of SoCs. That is an extended family. No need to make up something else. And pretty good chance Apple expand much from that breadth at all. [ Again the video of hiring selectively and for stuff to make unique stuff for Apple products. Coupled with Apple's re-use deployment in systems. 'M' in both Macs and iPads. 'A' in both phones , iPads , and AppleTV. 'S' in watch and Homepods . etc. etc. The 'R' is probably only temporarily an outlier ( if boondoggle Apple Car showed up ... good chance it would get tossed into it. ). ]