cmantis
Savannah Super Cat
Hopefully if you keep your kitten in the bathroom, you will be in there a LOT. If you don't have other cats and your loft is small, you can probably let him out of the bathroom sooner than two weeks, once he has settled in and seems comfortable with you and the move. What you don't want is for him to have free rein of the place and find all the best cubbies and holes to hide from you, so once he's coming to you on his own, and is comfortable knowing where the food, water, and litterbox is, you can probably let him venture out - supervised of course to start with.
If you have other cat(s) then I would stick to the two weeks (or longer if needed).
I do have another cat (same kind from same breeder). My place is all one open floorplan with lots of vertical space. The bathroom is not that big so I kinda feel bad leaving him in there for two weeks but if you think its best I will. Also will be kinda hard trying to split my time between the two cats as either I will be sitting in the bathroom with the new cat while the one I have is jealous or in the main area not getting that bonding time. So I am not really sure what is best. I do worry a bit about the new cat bonding stronger with my current cat then me though. Me and my current cat are super bonded.