They are central to Freljord's history. We saw a glimse of one in the Wonder Above teaser. But, do you think we'll ever have one become a champion? Bard, a being of cosmic relevance, just became a champion. Could one of the powerful Watchers do as well?
No, just for the fact that they would have to completely redo the howling abyss interactions. The Ghost's whole "I guard this place, least the Watchers return" would require him to not support the Watcher, and most likely take an active part in the battle. The other shop keeper would also have to get involved at that point... It would just be too much of a change.
I could see a Watcher showing up for a featured game mode though.
If we do, then no one can know that they are a Watcher. They'd need to change Lissandra's and the Howling Abyss quotes. If a Watcher returned to the world, then Lissandra could complete her plan that she's been waiting a really long time for. Lissandra would rule the Freljord, then use her accumulated power to bury the rest of the world. So no, sadly I do not think we'll be seeing the Watchers return (as much as I'd love to see them...). There'd have to be another Frozen Watcher separate from those that gave Avarosa, Serylda, and Lissandra their powers. Also, we already have a large number of Freljord Champions and Lissandra kind of covers the spot of "Powerful, Ancient, Frost Mage". There could, however, be another supporter or anti-Frozen Watcher champion. Say maybe one that told Avarosa of their intentions and caused her to rebel. Or maybe someone who's been alive for a really long time waiting for the return of the Watchers. Honestly, the lore is vast and amazing, there's so much they could still do with the Watchers. I just don't see an actual Frozen Watcher fighting on the Fields of Justi-... being a champion as it would conflict with a lot of character quotes.
And besides, do you honestly expect the lore team to actually do something that requires as much effort? It's easier to just make up a new story.
YES PLS!
I kinda doubt it,not only for lore reasons,but also for champion diversity.
Champs usually try to cover an archetype that isn't already present.
The watchers look quite like some kind of Beholder.....which is basically 
s thing already.
It isn't impossible for the watchers to be different(I mean they might have bodies,making them more like alien looking cyclopses),but then there are also the lore problems.
However I could imagine someone being posessed by some kind of watcher,you know someone who has a watcher sealed inside of him/her and where the watcher is trying to take over.
I could see them having one escape secretly. And it looks for a way to release the others.
The lore would have to make it sounds like it proved that it was not a watcher somehow. Thus the ghost wont do anything(but still be suspicious).
