Unfortunately that lens has two issues right from start. First one is, that it will be first and only DA* or * lens that does not have any sort of focusing scale, so in pitch black, dark night sky or with strong ND filter you are done as AF has nothing to catch and all you can do is do try/miss procedure multiple times.
Other issue will be price. I don't believe it will reach below $1600 or €1600 in EU. But is it going to be 3-4x better optically than mighty Sigma 17-50/2.8 which cost around $400 here?
Well well.... If Ricoh creates K3m3 + 16-50/2.8II kit and offer it for €2200.. I might be interested. Otherwise K3 & 17-50/2.8