Copal were still making leaf shutters until 2013, so one must assume the ability is there somewhere. I would hazard a guess that a 120 folder might be easier than a 35mm SLR but that's going to be a very small market, surely? Most of the photography students and people aspiring to do something other than lomography are looking for an SLR.
Thinking of Lomography, does any of their cameras have decent shutters with multiple speeds and apertures? I guess Seagull are still making TLRs. So a leaf shutter camera is not impossible.