There’s a runDisney Springtime Suprise race weekend evening event at TL on 4/6, so at least by around then at a minimum. But generally agree with the other posts.
Likely they will switch back by spring break. When we spoke to staff at TL on Saturday, they reiterated that just one park will be open at a time because it’s all the same staff. They just switch parks.
This year (2024) Typhoon Lagoon reopened on Sunday March 17th.
In 2023,Typhoon Lagoon reopened on Sunday March 19th.
If you're going by the past, in 2025 Typhoon Lagoon should reopen on Sunday March 16th.
They usually announce the reopening officially sometime in beginning of February.