The only non-88 key weighted action synthesizer that Yamaha makes currently is the S70 XS (which is 76 weighted, Balanced Hammer action keybed, with initial and aftertouch). It is the same synthesizer engine as the Motif-series without the sampler and sequencer (it has a playback only sequencer). It also does not have the same depth of editing from the front panel. The S-series is the Stage Synthesizer for those that want the Motif-series sound, in a quick easy to use unit. Full editing can be done with the free/downloadable "S90 XS/S70 XS Editor Standalone/VST".

Hope that helps. If you are asking about future products - we all will just have to wait and see. We don't/can't answer about the future because "who knows?"

Link: Current synthesizer line-up