Seems like they just disappeared. Heard that they were going to be MIL/LE only, but they were nice scopes. Not really liking the alternate lines Mk 6, Mk 8, and such. Why would they drop non MIL/LE from purchasing?
Strange.... I see some vendors still have them in stock. I went to Leupold's site and several of the Mark 4's listed say "No longer for sale" in bright red.
I see they're not available through the custom shop either.