I doubt there will be any synchronization with the electronic shutter. In Nikon Z6III it is 1/60. In the R6 Mark II, the electronic curtian speed is very similar to both C50/R6III and Z6III, but there is no synchro. Usually, even if the shutter is fast enough, synchronization appears when the sensor is "stacked" or "partially stacked".
"This is the last generation of full-frame cameras that will have mechanical shutters" - No, not the last. Maybe second-to-last, but I doubt the next generation will have fast enough sensors for that. In the $3,500-$4,000 class, yes, no problem, that's already there, at least for Nikon and Canon. But in the $1,500-$2,500 class, I don't think so. Also Canon still has an image quality penalty for its electronic shutter, even in their fastest cameras like R5II, R1 and R3. They need to solve this issue. That Sony sensor that S1II and Z6III use, also has some penalty. I think a sync speed of at least 1/180 is needed to get rid of the mechanical shutter. I doubt they'll triple that 1/60 in a single generation. I also doubt they'll just give top-end stacked sensors to $2000 class. To do this, they need to come up with something cool for the $3,500-$4,000 segment, and I doubt they have anything.
In fact, I would be happy if in the next generation they slowed down a bit in their rush to make sensors faster and tried to restore the image quality that they sacrificed in this race.