Challenge is most certainly in business, albeit not at the level of a few years ago. Paul Voerman's departure did leave quite a hole in their output.
Arnold Ligtvoet is busy not doing Raptobike; I think he was doing some work for Optima after Elan took over Raptobike, and has been mostly branching out with other engineering.
Personally speaking, I'd pass on the Schlitter and go for the M5 CHR. The seat height isn't too lofty, and given a few hills the bike will deliver average speeds not far off those of a velomobile.