As clearly stated on our "Home Page":
"Because of the success of the previous Misty Moorings, Inc website for FS2004, we have been asked by many of our previous fans to create an FSX, FSX-DX10, Prepar3D version. This is it!"
Therefore, RTMM is a massive website and community of users dedicated to flight simulation based on the MS FSX and LM P3D platforms, as well as being centered around the prerequisite ORBX and TF base scenery regions. Period. Based upon that underlying criteria there are no plans whatsoever to expand into X-Plane and never will be. I'm sure you can find X-Plane scenery in abundance elsewhere.
An even bigger reason for not making RTMM scenery for X-Plane is that none of the RTMM team of developers and support staff even own X-Plane, yet alone even know or understand how it works. It's taken years for each of us to learn the ins and outs of MS based flight simulators. For each of us it's been huge learning curve that's literally taken years and enormous amounts of money invested in related software! I personally started learning what I know by learning, working and developing in MSFS5, MSFS98, MSFS2001, FS9, FSX, MS Combat Flight Simulator and MS Combat Flight Simulator 2. Knowing "what's under the hood" in order to do what we do as a team has been a HUGE undertaking for all of us.
An X-Plane and RTMM marriage isn't going to happen unless you want to do it and then make a presentation to the team for an evaluation.