You can already do this believe it or not using http.
I really want us to not have to.
I know it’s possible currently, it’s really cool to see it coming as a feature though. I just want to know whether or not a live player count will come with this.
Probably not. I tell another server my player count – cool – it knows our combined player counts. Now I have to do that for every other server. There will probably be a rate limit, so you won’t be able to do this unless your game is small and doesn’t have a lot of servers. Even then, you have to aggregate all of that and coordinate which servers get which information, making it more trouble than it’s worth.
So the distinction here is that “Universe Scripts” were expected to be a Peer-Server-Peer type of system, but this “Cross Server Messaging” will only be a Peer-Peer system, right? Shame, I think the biggest reason I was excited for Universe Scripts was because of the fact that they could (in theory) centralize everything in one place.
I only came back because of universe scripts… 
Welp, I’ll hibernate for now.
I’ve noticed that on the Roblox Roadmap, the feature “Universe Script & Game Services” has been completely cancelled. Could we get anymore information on this? Is it just being pushed back another quarter, is it only cancelled for this year, is Roblox completely throwing out the idea of Universe Scripts? I really need some more information regarding this, since a game idea I’ve been having for a while completely depends on the idea of being able to make real matchmaking between players.
This appears to have been switched to “Postponed”.
Based on the description in the release notes, yes.
MessagingService provides a Lua API by which developers can communicate between servers in near real-time.
Cool stuff with all the UI updates planned. 
What UI Update? I read through the Thread but I think I missed it.
We should at least know if Universe Script & Game Services is going to come out, or Cross-Server Messaging is going to replace it entirely
We have been waiting a long time.
Since the thread has been bumped I just wanted to toss out that I really hope Roblox keeps the roadmap more up-to-date.
A development roadmap is an extremely powerful tool to communicate with users and developers what you are working on, and I used to refer to it religiously when I wanted to look into what new features where coming up and when to expect them.
Sadly we now are seeing features that were targeted for 4th Quarter 2018 still showing as “On track” even though we are half way through 1st Quarter 2019. I hope to see the roadmap updated again soon to show the current status of development and set forward some expectations for 2019!
I think it’s safe to say that this roadmap isn’t very trustable at this point. Two “On Track” releases are from 2018 and all the new stuff that has been releasing isn’t on the roadmap at all such as dark theme etc.
Except Dark Theme is on the roadmap, it’s the first thing on there. " Targeted for 2nd Quarter 2018 (April-June) → Dark Theme for Studio" Dark theme was made back in the time that the roadmap was being actively updated.
Stuff that is still recent and being worked on is on there too like FiB and Mesh LoD.
The fact that it hasn’t been updated though since last quarter is disappointing. I’m hoping they value updating it again.
Dark theme for the website…
There is a dedicated thread for requests for the roadmap to be updated:
Please respond there if your question/comment is related to that so we have it all in one place.