To be honest, It's become stale due to the lack of proper changes to the layout and theme throughout the past few years of the Terror Tram; with a tedious sense of doing the same thing over and over and over again for many that have went to the event (much like the definition of insanity..). Plus, we also have the Metro Sets since 2013 which have been starting to potentially be not enough space for an area like that with three mazes interlocked with eachother.
Heck,I may have a legitimate reason for the Terror Tram to potentially depart is something that I have found possibly interesting. With the three mazes down there, they may want to mainly relocate a tent so that way; there may be a better flow around the metro sets in the sense of the line operations. In a sense, relocate the tent seen for Krampus/TWD/CP through the past few years up to a area next to the repair bay and house the line in the entire Studio Tour queue line and some bits of the load and unload sections. It wouldn't exactly need changing, besides some aspects to it; and it can hold a lot of individuals given the potential chance, depending on IP of-course.
Could that happen? Yes. It'd allow a much easier way to manage the flow of mazes throughout the park and to not just saturate one area with three mazes so close to eachother. And as for the case of the Upper lot, it's not like all the mazes that'd be there (WW Overflow, TWDA, potential Studio Tour location) would be close to eachother. Each would be separately but equally spreaded out to ease the flow all around. To me, that could actually be the most sound proof reason to why they may do that. Along with that, it could also allow more money to be put into the event to things that matter more in a sense with Terror Tram out of the way.
It's the way i see it personally, but it's my own opinion.