It would be interesting to see something like this (all theoretical):
MB12: Apple A13X or A13M, 8 GB, and a powerful Apple GPU (PowerVR Based, of Course)
or Ice Lake at a very low TDP + T2 chip
MBA13: Intel Ice Lake Y i5/i7, 8/16 GB, Iris Graphics, T2
MBP13: AMD Ryzen 5/7, 8/16/32 GB, Radeon Graphics, T2
MBP16: (Here's where it gets interesting...)
- Base Model: Ice Lake/Tiger Lake with JUST Iris GPUs, and maybe 16 GB only, or AMD Ryzen 7 H-Series (could even be semi-custom) with Radeon graphics onboard and 16 GB only, perhaps $1699-$1999, and limit the storage options, essentially make this like the Mid 2009 15" base model, and the 2013-2015 15" base models
- Upgrade Model: Whatever Intel's fastest is, plus whatever the latest AMD GPU is, basically more of the same.
It would be cool to see the T3 act as another processor and do more background tasks, or even being able to run the OS at idle or while doing things like video decode, to switch off the main x86-64 CPU and save a lot of power. The T2 already probably has a built in GPU (for the touch bar), and could function as a chipset. Perhaps an A-Series chip would be better for that, especially if it could replace the T-series, such as "A13M" for Mac that combined the capabilities of T2 with the cores and more powerful GPU of the A-series chips. All of this would rule out hackintosh within a few years, but luckily Apple still made macs without the T2 as late as 2017 (the fn-keys MBP13). Pros want the x86, but for people just watching Netflix on their couch or on a plane where battery life and lightness are key, macOS running on ARM would really be the way to go. But first, fixing those keyboards...
EDIT: We could also see x86 and ARM cores on the same chip, ad AMD uses an ARM core for their Platform Security Processor and Intel does something similar by using a Quark based CPU. Multiple architectures can exist on the same chip.