I don't think Cross-X is quite done yet and still has lots of valuable discussion.
That said, I would also like to put in a positive word for /r/policydebate (full disclosure, I am part of the modteam). I don't really use discord, but from my understanding I don't think that the discord and subreddit really trade off with each other, but rather fill different roles. That's actually why we link to the discord on the subreddit sidebar, though I'm not sure if the discord does the same vice versa.
I think that Discord has some really strong potential for vdebates and casual discussion about debate and from what I've gathered from the above posts, some really interesting resources. That said, discord and other chat mechanisms are a much bigger departure from forums like CX and thus risks losing some of the benefits, things like long advice posts and more in-depth discussion. The discord is also a few hundred people smaller than the subreddit.
Another advantage that both /r/policydebate and probably the Discord also have over cross-x.com is responsive modteams that takes concerns of users and reports seriously.
I encourage you to check both of them out! As some examples of things that /r/policydebate has to offer, there's
In-depth topic discussion
Detailed research tips from college debaters/coaches 1
And of course, memes