I will have to agree with Loren, its not a matter of when, its a matter of if they will make it. Given the current stance of MTL, it doesn't look like they are putting effort into Z any longer?
...I strongly doubt that... the GP35 Maxon fits perfectly for a switcher. David K, David F, Gerd and myself (and who knows else have tried this) here on Trainboard, have already proven that it can be done. I am using my SW1000 now for 6 months without any problem.
the chassis could even be shortened to fit in F7 A & B and could be used unmodified for an FP7A or FP9A so there is lots of room for this motor in many variations of the GP9/35 chassis. shortening the chassis at least to fit the F7 shells is easy, it takes a bit more to shrink it for an SW or MP but all very doable. I will have my FP7A and F7B at Atlanta both have Geep chassis or modified Geep chassis. modification to fit F7A and F7B will still accept the TCS MZA4 decoder even after modifying the chassis.