To get back to the original question- it's possible we may get saunas outside Glasgow but not likely IMHO.
When Edinburgh stopped licensing them, and the bad ones were weeded out, I at first thought there was no logical reason why they couldn't open up elsewhere after a decent interval.
Remember, the Edinburgh ones are completely unlicensed and the police (despite some bad press at the time of the raids) are presumably now turning a blind eye to the fact they're brothels, as long as there's no trafficking, drugs or under-age stuff. And since it's a national police force, that blind eye, in theory at least, should apply everywhere.
So, if one were to open tomorrow in Glasgow and it was all ok as far as planning/environmental health/trading standards was concerned, the Council could do hee haw about it. The police, if they were to get complaints from the council/public may then say they were responding flexibly to local concerns and go after them as brothels-or they may have better things to do.
But-there's too much uncertainty in all the above for anyone to sink the huge investment needed for a brand new venture to be ok planning etc. wise and then get busted on day one.
The best prospect may be one of the current semi-legit massage places in Glasgow being bought over by the owner of a current Edinburgh one (who the police are presumably ok with) and then the services being slowly and incrementally expanded, as happened originally in Glasgow over 30 years ago. Some of us are old enough to remember the "Any extras?" question.
But as far as brand new ones appearing suddenly, we're left with that uncertainty, which means it probably won't happen, at least in the foreseeable future. So, I'll have to keep going back and forth to Edinburgh for a good while yet.