I feel like Urouge is either going to show up on Elbaf, or somewhere else pretty soon. There is some speculation that we could end up back in the Sky Islands after Elbaf. So, if Elbaf's World Tree is actually the "Summit of High West" that Gan Fall talked about, we could meet Urouge back on a Sky Island.
There really aren't too many islands left in the story. So, either it's going to be Elbaf, a Sky Island, or maybe Lodestar.
I very much doubt Oda would save Urouge for Laugh Tale, since he doesn't strike me as being THAT important. And I'm not sure if returning to the Sky Islands is a very likely development or not. We don't have a lot of reason to go there, other than MAYBE to bring Enel back into the story. So, Elbaf and Lodestar are the two most likely places where we could see Urouge again.
And given how Urouge is associated with "religion" by virtue of being the "Mad Monk", I think Elbaf is the most likely place we'll meet back up with him. Elbaf seems to a place that worships Nika. And it's probably where we're going to find out a chunk of Nika lore. I think it makes sense for another "religious" character to show up during a arc where we're likely to learn about the Giant's religion.
As for being a friend or a foe? I'm betting on friend. If only because, at this point in the story, the Strawhats already have so many enemies that I'm not sure if we need to be adding the the rogues gallery. Which doesn't mean Urouge won't fight the Strawhats. I could see Urouge "testing" if Luffy is really Nika or not.
...Or Urouge could just end up getting jobbed by Enel, if Enel is coming back into the story. We've had some hints that those two have history with each other. So, maybe Urouge could get defeated by a powered up Enel?
So, he's probably going to be more of a friend on Elbaf. That's my best guess.