Here’s how that works, direct from the bellowing bearded faces of the developers themselves.
By which I mean, a new Steamblog.
Keep it clean, though - there may be elves reading.

The new approach to Deep Rock Galactic seasons brings with it a new approach to cosmetics.
Existing Performance Pass and Cosmetic Tree progress in each Season will be preserved after Season 5 launches.
The developers stress that the upshot here is that for most players, nothing will really change.
It’s just about reorganising the fixtures.
Ghost Ship have many plans for the Deep Rock universe, with several projects in the works.
There’s the November 2024-boundDeep Rock Galactic: Rogue Core- a roguelike spin-off, as you’ve probably guessed.