Nintendo isn't launching anything on a Saturday or Sunday
If they decide they want to make Switch's launch such an event where the thing launches on the exact same day in all three major markets and countries, we could actually see a Saturday launch even if Nintendo's now used to release stuff on Friday in both Europe and US (Thursday in Japan is the classic day for everyone). That's because Saturday is when major launches happen in Japan: games like MH, DQ, Pokemon and brand new hardware as well.