TW would have to start making dramatic improvements to rebuild the player base such as overhauling Skirmish to be more akin to battle.
It's possible that their "one life mode" can achieve this. We don't know who is designing it, but it has a reasonable chance to bring players back at least to try it out. If TW's version fails, it's also possible that TW adopts the competitive standard (when it is determined) and hosts the official ranked ladder on that format.
On the other hand, Captain queues are fine. They're faster than my Overwatch DPS/Support queues. But due to well over 50% of units needing balance changes, Captain isn't the most fun to play, but it's clear that TW has found the core of something with the player retention against BLO.