To be honest, it is so much easier to perform edits such as "crossfade looping" on a computer that the comparison to trying to do it "onboard" creates more problems than solutions, especially when trying to edit multi-sampled instruments. Our good friend John Melas has created such an elegant, powerful and amazing solution with his Waveform editor that if you ever experience using it you will not want to manage, edit and even create Motif samples any other way. And for what it does, it is not that expensive. Check it out at http://www.jmelas.gr.
So I discovered why Yamaha will not release a new OS to introduce "crossfade looping" in sample edit for Motif XF. It's to force us to get this program Waveform Editor. Such deplorable posture of Yamaha. Even Korg Triton series, M3 series and Kronos series got this function, but Yamaha Motif XF, a premium product, lack this important tool. So sorry, but it's my opinion.
Yamaha is not forcing you to buy John Melas products...he is an independent vendor, not part of Yamaha. Waveform Editor has a lot of great features that make managing my XF a lot easier. It was well worth the money.
It is unfortunate that over four generations of Motif crossfade loops are still not supported despite numerous requests for it, but it is what it is. I'm not losing any sleep over it. There are free audio editors available you can use to do crossfades if you don't want to pay for one.