We were too clever for our own good. We had a few very excited customers, but not enough. There might be more these days, but we are not going to take the risk to create the next generation until its clear the folks want a $500 expression pedal.
Yea, that makes sense. Time after time, Source Audio runs headlong into the wilds beyond the bleeding edge of possibilities-- you're bound to have to walk it back from time to time as the market isn't ready for it (cost-wise or concept-wise). Perhaps at some point, when you've got some breathing room in that hectic schedule there at SA, you could consider some kind of crowd-funding-pre-order-- with a pre-determined threshold for number of pre-order commitments to meet your goal.
Alternatively, I could imagine an SA device that has two pedal inputs; expecting specifics like 1/4" TRS, 10K, wiper on tip-- (pedal not included). It could have 2 pedal outs, MIDI IN and MIDI THRU/OUT (merged), maybe 3.5mm TRRS i/o on top/back. All that could follow the shape format of one-series (like EQ2). Within the Neuro Editor, users can adjust routing, global adjustments for the input range (min, max) & user-drawn curve, preset-by-preset output range & curves, resolution (select 7-bit or 14-bit CC/RPN/NRPN), smoothing, thinning (to prevent MIDI data log jam), maybe even some modes for connecting switches.
I have a product from AudioFront.net called MIDI Expression iO which has 4 pedal ins, USB i/o and MIDI din i/o. It covers some of these bases, but only via MIDI & USB, not pedal outs-- which seems fairly rare, but useful for nerds with FX that have EXP ins.