it's all on git: https://github.com/RetroPie/RetroPie-Setup/

follow the commit messages and PRs and you can see what's being developed. beyond that, there's discussions going on behind the scenes, but there's no formal roadmap. remember this isn't a job :)

Good to hear all is working well!

I still need to buy a Pi 4 so it will take some time for testing it out..

Thanks for the support!

Great news, will do ASAP!

@Brunnis said in No Raspberry Pi 4 in 2019.:

I'll be getting the 2GB version. I just don't see the point in getting the 4GB version unless you're going to run desktop type workloads or know, specifically, that your workload is memory intensive.

More RAM is also useful for speeding up repeated hdd/ssd/sd access, since Linux uses unused RAM for buffering the file system. You can see this via the command free -h ("h" means "human readable" for more human-friendly numbers). Example from my Laptop:

total used free shared buff/cache available Mem: 7,7G 2,2G 2,5G 405M 2,9G 4,8G

Although the "free" memory seems to be only 2.5 GB, temporary buffers take 2.9 GB. The real amount of free RAM is 4.8 GB, since the system clears the buffered data as soon as the memory is needed elsewhere. (Don't ask me why the numbers don't seem to add up perfectly, I don't know the actual math behind it.)

I don't see it in any way different than other SBCs based on the RK3399 - there are countless ones released recently (like the Rock/Pine series). The XU4, despite being 'older' I think it has better support as far as RetroPie is concerned (i.e. emulators tested, graphic drivers, GPIO, etc.).
Do note that a better CPU and better graphics usually mean also you need a cooler/heatsink in these cases.