With how wrong things have gone to date, I'm just going to say it will take whatever amount of time it takes. It's a hobbyist project being done by people with jobs and lives and things don't go to plan. With my luck I'll say 5-10 a week sounds reasonable, and then he'll break his hand, or my house will catch fire or something. I've knocked on wood enough there's a hole starting in my desk...
At least in this particular instance (with the exception of maybe 3 or 4 people, and of course myself), no one is out anything beyond the cost of the donor cart during the wait. Which I'd like to think is a big step up from how most projects in this hobby go. Especially the ones in the classic arcade community where it takes 3 years to remanufacture a piece of metal and you're out $500 that entire time.