Looks like MK20FX512VMD12 would be the likely part number. At first glance, it looks pretty much the same as Teensy 3.6 without the HSRUN mode (for 180 MHz) and Ethernet.
And the answer to your question is most definitely no, zero chance a Teensy 3.x will be made with that chip!
Like all the other Kinetis K20-K60 chips, it's basically not available. We ordered large numbers of the chips for Teensy 3.2, 3.5, 3.6 in early 2021. Here we are at the end of 2022 and the latest updates from NXP are showing only a small number coming in 2023. Whether we get the rest in 2024 or even later is still uncertain. For all practical purposes, NXP just isn't able to make these chips in the foreseeable future.
Even if we could get the chip, without major work the software support would look very much like Teensy 3.6, with device mode supported on the full speed port and host mode on the high speed port.
But even just supporting it as Teensy 3.6 would involve major work which we just can't do right now.
Teensy 4.0 and 4.1 have 480 MBit/sec USB, on both device and host ports. They also have much higher CPU performance, which makes actually using that raw USB speed much more achievable for demanding tasks. And best of all, NXP is actually sending those chips, so we can really make Teensy 4.0 and 4.1. Both are in stock today and we're anticipating pretty good supply in 2023.