There is a substantial unsatisfied demand for the UJM type with all the modern technological improvements. Able to cruise comfortably without being a heavy cruiser; responsive handling, without the discomfort of the cafe' ergos. Triumph has come the closest to meeting that demand, hence, their success with the classic line.
I really think that is the case ie: UJM unsatisified demand. I think Kawasaki's earlier W-650 introduction failed due to inauspicious timing (and a slightly too small engine) because of the big jump in popularity at that time of the heavy Cruiser type, Harleys and the continuing demand for racer boy sport bikes, all 3 of which have since waned quite a bit in popularity IMHO.
That popularity rise seems to have been driven by new riders many of whom now know the difference and would now like to get a sensible, comfortable bike.
Because the Kawi W-650 failed first time out everyone now points to that case as proof that a UJM standard "classic" type can't sell in North America, more's the pity. Evidence of this is Honda's (stupid) refusal to bring the new CB-1100 over which looks to be the epitomy of modern, standard UJM.