Stop by this thread if you like to show support for the old War Chest content. It’s been running for a while with a lot of views.
SC2 is still supported. What’s been discontinued is development of new, paid content. And depending how deep one reads into that, it could mean discontinuing all new development, paid or not.
But either way, you’re right. It’s possible Blizzard isn’t interested in providing the old War Chest content if they are done with new SC2 development.