Your current character will be forced to sit on the bench.
What happens to your characters, stash, and gold when Diablo 4 Season 1 ends?
Blizzard confirms the need to create a new character every Diablo 4 season - Xfire
All NEW Players Need to Know This (Diablo 4 Eternal & Seasonal Realms)
How to create a Seasonal Character in Diablo 4
Blizzard confirms the need to create a new character every Diablo 4 season - Xfire
What is a Season in Diablo 4? - Wowhead News
Diablo 4 seasons & battle pass require starting a new character — why? - Polygon
Diablo IV Will Make You Create A New Character For Every Season
What are you playing in Diablo 4's Season of the Malignant?
Diablo 4 player achieves the impossible by hitting max levels for all seasonal characters - Dexerto
Diablo 4 Season 1: Launch Times and Everything You Need to Know