After announcing the Switch ports of both La-Mulana back in August, NIS America has confirmed that the double pack will be launching in March 2020.
Specifically, North America will see the games launch on March 17th, Europe will get them on March 20th, and Oceania will be last to pick them up on March 27th.
Pre-orders for the elaborate Hidden Treasures edition are also still open via the NISA Store, so be sure to head on over and grab that if you want some physical goodies to go alongside your tough-as-nails metroidvania!