My prediction is an A-series Mac won’t start from the bottom up it’ll start top down - beginning with a Mac Pro addin card.
Imagine a future generation T-series chip with the neural cores that the A-series chips have. Accessible using the existing frameworks that you are already using. Or adding GPU cores to the MacBook Pro lineup as a replacement for the AMD GPUs that they have now.
And while they are doing that, they can release a Smart Keyboard for a future iPad Pro that has a trackpad. That's got to be one of the least risky ways to try out the iPad as a laptop replacement. If it's a flop, you're out the $150 or whatever it would cost but still have a perfectly good iPad that you keep using as an iPad.
Apple is in the position to take a "lets see where this takes us" approach. As long as they keep the OS and Frameworks from drifting apart, there are a lot of nice things that could happen.