If I remember correctly there was talk that Rumba was set for an overhaul for next year, so that may be way!
An Overhaul as in retheme like Dragon Falls is going under or overhaul as in refurb like Hex went under? I wouldn't think a retheme is too likely as Merlin wouldn't want it to clash wit Tiger Falls. However refurbs are nice when you have done to the standard of Hex and AT's Driving School.
Also wasn't it mentioned in the Project 2020 thread that Thorpe was taking a year out for general improvements could 2018 be the year as we haven't seen any planning app or rumours of something new for Thorpe.