I agree with many of the comments already made here about Roland and Korg. Neither will ever let their products be "softsynthed", no matter how good the emulation, as they are big enough that they would rather do a "less good" imitation and milk their old glory for all it is worth.
Sad but true, so no Jupiters, PS 3X00 or the like....
The key is to find a unique instrument to emulate, or emulate something in a manner which it has not been done before.
One big hole in the industry remains the simple big american polysynth. The Prophet has been emulated, but IMHO not as well as it could have been, and certainly not with the typical refinements which Arturia does so well (the extensive modulation routings etc.).
Personally, I am still waiting for someone to give me a sound that will actually allow me to leave my OB-8 at home for my next gig (and believe me, as I get older, size and weight is becoming an issue!!). Overall, I think the Oberheim sound is where Arturia should go next.
With that in mind, everyone is revved up on the Oberheim Xpander. What is good about this instrument is NOT its sound generation technology (lower class of Curtis chips), but its extensive modulation routings and filter choices. The true "Oberheim" sound lies in the OB-X through OB-8 synthesizers, and owes a lot to good engineering, and good quality chips.
Why not develop an instrument based on the sound generation technology of the OB series (fast "hardware" envelopes, higher quality Curtis-style oscillators and filters, simple "panel" routing options), and build in the modulation routings and additional filter settings of the Xpander (also capable with the better filter chips, with a little work!) lying in behind?
Essentially, what you would have is an instrument capable of producing typical OB series sounds (big brass, lush strings, fat bass, searing leads), but can also produce the complexity of sound from the Xpander. Trust me, if money and hardware size were no object, I'm sure the lads at Oberheim would have built the Xpander out of the higher grade chips!!
You could even have the software version read sysex data from the Xpander/Matrix series, although the sound would definitely be "fuller" than the original if an A/B comparison was done....
The CS is the ultimate in Japanese analog polys, now lets get a big unwieldly american model in there!! (and no, I'm not from the US!)
Keep it up Arturia!!