Okay so lost in the hubub about the 2018 12" all-digital cluster is the fact that the REGULAR clusters on the 2018's all have a digital speedo (like the GT350) now.
I believe this should mean that we could possibly flash the 2018 IPC firmware to a 2015-2017 cluster, flip some bits in the as-built and have a fully functional IPC with speedo.
A few guys have already flashed the GT350 firmware to their regular IPC to get the digital speedo, but that has a ton of drawbacks. I would think the 2018+ IPC firmware would work without issue.
Already tried that but the hardware is different between the 15-17 to 18...