Uhhh...Apple has been ignoring the Professional community for years. Yes they have released a couple systems to not completely abandon them but they are clearly more focused on Phones, tablets, and laptops which get refreshed yearly, vs professional computers like the Mac Pro line which took 6 years to see an upgrade. Maybe that changes with the move to Silicon but if recent history is any indication I wouldn't bet on it.
As far as eGPUs, we can say with a lot of certainty the current eGPUs that are built around Intel chipsets won't work as is.
Best case scenario is we have something similar to the PowerPC days where we can "flash" an Intel card to make it work with silicon.
Worst case scenario we have a situation where the architecture is too different and the eGPU is some sort of Breakaway box that is built solely for silicon systems which means there will only be a couple expensive options because 3rd parties are not going to line up to build something for such a small community.
Worst worst case scenario, no eGPUs with silicon.
I guess there is another best best case scenario in that silicon is so powerful and awesome eGPUs aren't needed.
They
were ignoring the professional community for years and then they turned that around with the iMac Pro, the Mac Pro, Pro Display XDR and you can even argue the more recent 15 and 16 inch MacBook Pros. Heck, even the Mac Mini is more pro than it used to be. If you're looking at the last 10 years then I understand your trepidation but if you look at even more recent history, as in the last 3-4 years, they're throwing a whole lot at professional users.
Current Nvidia GPUs already work with ThunderX2 ARM processors, it isn't a big hurdle to get current GPUs working on ARM. I am certain we will see great graphics on the low end without discrete GPUs but on the high end there will be iMacs and Mac Pros with a combination of Apple silicon and proper GPUs. The only real question is
when in the transition this happens, not if.
I also don't believe that Apple would be pushing eGPUs so hard since 2018 only for them to abandon them to Intel Macs alone. They have a plan for eGPU usage.
I'll make a prediction here and you can come back and tell me I told you so if it doesn't pan out lol.
The first ARM Mac Mini (assuming it is released between now and next summer) will match Intel 6-core 10th gen processors, it will have built-in graphics better in performance than an Xbox One/PS4
and it will support eGPUs. If it is released later than that we can assume it will have even better processing power.