RISC-V first class support.

We have the basics down. But hopefully desktop-class RISC-V will be within our reach in a few years!

Immutable root filesystem.

Less user error from borking the root fs. And also less apps relying on the root filesystem would be good. Likely something to be achieved with portals and other XDG work.

Wayland only for all modern desktops.

Wayland will soon have the ability for a lot of cool features that X11 doesn't have, such as storing session data to disk and relaunching into new desktop environments without relogging. This'll make hybrid graphics a lot easier to manage as changes to the active GPU can be done dynamically without logging out and back into your system.

Greater adoption of XDG portals and XDG standards.

Linux is obviously great in many ways because it lacks a single solution to a given problem, and that it's just a kernel, so most of your end-user system is totally configurable while still being a Linux system. However, we have a lot of overlapping work that makes said end-user systems hard to manage when standards collide. Hopefully Wayland will encourage developers to work through XDG portals and other common standards to make Linux user AND developer-friendly.

Nvidia drivers

A contentious issue, but I think the future of Nvidia drivers will be open source. The proprietary drivers have been a blocker in many ways as they're 'good enough' and better than Nouveau, so no one is going to bother backing the FOSS project when the prop. project is better. However, lots of very smart devs are working on bridging the gap and leverage the newly open-sourced portions of NV's drivers, which will hopefully manifest as the end of AMD/NV driver quality discrepancies.

WINE support improved for general desktop apps

Every few years we get a new "Photoshop WORKING on LINUX???" tutorial that has some cryptic setup instructions or github repo that eventually falls to the wayside. WINE is getting a lot more support thanks to Valve and I imagine starting to take on Windows apps for first class support will be a gamechanger for the creative industries that rely on certain Windows-only apps!

Ending the distro-specific packing systems.

Yup, the best saved til last. My boldest claim is that Flatpak is going to kill off the necessity for RPMs, Debs, APKs, etc. for most end-users. The flatpak size disadvantage is negligible in the age of terabytes, but it allows devs to ensure a consistent build environment for their apps on all platforms (something that has caused a lot of flame wars between Fedora and app devs in the past).

For people who DO need apps from reproducible, stable-based pipelines (eg. docker, sysadmins, IT professionals) we'll see Nix becoming dominant. In fact, it's already beginning to eat into docker/container build systems thanks to its powerful reproducibility and infra-as-code paradigms. It's having a real boost after a relatively quiet first decade of life, likely thanks to features like Flakes that can spin up developer environments in seconds.