No lol and I don’t think many people are putting that as prio on their feature wish list. It’s already a resource intensive game, and there is a lot of room for improvement, as they’ve been showing off with these vids lately.
I guess it could be cool to view/link cities, but I don't see much value beyond that. If that's wanted, it could be added pretty easily later on.
But if you want multiple people modifying the same city, I fear there would be too many issues that the sim would have to be more shallow. You'd need to target the lowest common denominator so the MP experience is consistent across hardware, and then you'd only get the performance of that lowest common denominator to keep things in sync. It seems they're going for more depth in the sim and more performance, so adding in MP would go against that.