The linked blog post https://www.raspberrypi.org/blog/new-product-raspberry-pi-3-... has more info and is interesting.

In it they say "Back in March, we explained that the 3+ platform is the final iteration of the “classic” Raspberry Pi", I've tried finding the corresponding blog post but didn't have any luck. Does anyone know where I can read more about this ? I'm interested in hearing more about their need for "new core silicon, on a new process node, with new memory technology".