I dunno, I think I agree with Ian here, I'm not sure how much more they can improve the next S series, as with T4 and T5 sounding extremely similar, I fear the next S series will follow a similar pattern. Who knows though, they might finally introduce touch screen? The S series got the first look with Audio Drums, touch screen might be next as a tester. Or maybe just another 25 extra Audio Styles?

I like the idea of Audio styles but as an option, not a replacement especially if they're locked down. Switching between audio and midi drums within same style would be a really cool feature and you also get to keep them. Not sure if that could ever be possible though.

Thing is, if you become attached to those Audio Styles you stand to lose them with each replacement, that is if they don't already feature in the replacement. At the moment it's not too bad as there's only a few but in years to come when Yamaha might incorporate all audio styles, unless people know a way to hack the OS you'll lose those styles you might get attached to.

If the next S series has vocal voices from the T4 then I might consider an upgrade as that's the only weak attribute of the S950 (only my own opinion though), I don't mind losing the 25 audio styles that I don't use anyway, but if the number increases people might be reluctant to upgrade if it remains locked down.