Perhaps the next step is a 76 SX series, now that the advantages of those extra keys is being willing to be admitted! I for one would quite welcome a 76 SX900. As I really like playing piano parts with both hands, the extra octave or so makes all the difference..!
Not gonna happen.
Genos design is already compact and light weight for TOTL arranger. I believe they did it due to chronic complaints for poor bulky designed Tyros series and trying to complete with better cut/looking Pa3x/4x. I prefer Yamaha style control buttons because they are more solid and proven Tyros style buttons with good spacing. Pa3x/4x looks more stylish / cooler and the body construction feels more solid.
Sx900 keys ( even though they are improved), they are not the same category as Genos/ Tyros/Pa4x quality.
Genos , which has 76 keys (13 Kg- 28 lbs) is lighter than Tyros 5 - 61 keys which is 14 kg. It’s lighter than Pa4x - 61 keys which is close to 14Kg.
Width is way shorter than bulky fat Tyros 5 -76 and even 17mm shorter than Roland BK9.
Sx900 is already more than 25 Ibs. 76 keys with ( with supporting body )may add minimum 1 more pound with will be close to 27 lbs.
The problem with Genos is the price.