The after hours events are cash cows for Disney. I don’t foresee them being discontinued. They may change them up, add or remove but they aren’t going anywhere.
My guess is Sweethearts Night is fairly popular so will occur in the coming years.
The Disneyland After Dark webpage was updated a few weeks ago with messaging for visitors to look forward to Pride, Star Wars and Sweethearts' Nite parties next year. The only one apparently not returning in 2025 is Disney Channel Nite.