Either Chris or Tracy has firmly stated that DSI will never use miniature keyboards on their instruments. As for length, I do personally like having the variety that DSI offers. I think it's some times handy to have instruments with only 3 1/2 or 4-octave keyboards. They can compliment a corner of one's set up where room may be lacking. But the 5-octave keyboard reigns supreme with me for offering a full range for playing, while not being as immense as a piano-length keyboard.
If some of us are a bit impatient over keyboard length, it's understandable if you consider how long it's been since DSI last produced a 5-octave keyboard: all the way back to the Prophet 12. However, I don't think there's reason for concern. 3 1/2 octaves makes sense for a mono synth like the Pro 2, and 4 octaves makes sense for small poly synths like the Prophet-6 and OB-6. Again, that's for small poly synths, which is how I regard those two synthesizers. And that's why I didn't chose them for expansion with modules - they're just too small to start with, so that the end result would not be worth the substantial expense.
It's positively time for DSI to produce another poly synth with a 5-octave keyboard. This was the case anyways, but it's all the more true now, in light of the discontinuation of the Prophet '08. DSI needs something full-scale other than the P12, especially since that instrument is not appealing to quite a few serious synthesists. I'm hoping we're very soon to see such a new instrument - preferably in just a couple of weeks. I wouldn't seriously consider buying anything other than such a large keyboard synthesizer, and until it appears, I'll happily work with the four five-octave instruments that I have.