Three octaves isn't musically limiting if you decide to compose within those three octaves and that suits you, or if you carefully pick from a three-octave musical repertoire. But then again, that's...musically limiting.
I've recorded a mere three pieces with my Odysseys, and each one required four to five octaves. It wasn't my objective to cover such a range, but given the freedom to do so, I was happy to have it available. It comes down to style of music, of course. Much rock soloing fits within the shorter range, and that's probably one reason people are content with the length. But what if you're not a rock musician and you compose a three octave-range melody and then want to transpose it up or down a fifth or an octave? Too bad. That idea will have to be denied. And that's what I would like to avoid - musical instruments interfering with musical inspirations.
My point about this keyboard range is simply to have at one's disposal a fuller musical potential, so that, if you need the keys, they're available; and if you don't, then maybe you will later. But there's no harm in having them there. That an instrument is monophonic changes nothing, since monophonic playing can entail all sorts of elements, such as arpeggios, that may require five octaves or even more.
I have no interest in seeing my five-octave preference imposed. I realize there are other concerns, such as studio space, rig arrangement, weight, and portability. It's just that I know whenever Sequential produces a three-octave mono synth, I have to look elsewhere. That's sad, because I love Sequential's sound and designs. I would much rather have bought a couple of Pro 3 Modules and controlled them with a five-octave keyboard, but they don't exist. And if the alleged forthcoming Pro One reissue has the expected keyboard length, then it's still back to Korg for me.
I think a happy compromise for a monophonic synthesizer would be a 3 1/2 octave keyboard, like the Pro 2 and Minimoog. That would probably keep the greatest number of us happy. But three octaves? Three is truly three only if you're perpetually playing in the key of C. Oh, you need just on low b-flat to finish the piece? Sorry.