I think the second part will last 24 episodes, because the manga is still out and we know THIS is the last season. Although the manga seems to have reached its end, it seems unlikely that 16 episodes, as in part 1, will be enough to cover the entire final part of the manga.
Part 1 did 2 chapters per episode roughly, and not to rain on your parade but unless they do 1 chapter per ep and then some like filler... I don't think part 2 will be 24 episodes. The chapters are long but I think it can honestly be covered with 12-16 episodes as that seems to be the pace of the final season part 1.
Considering its part 2, i imagine that means together they'd add up
with the first part to be 24-26 episodes long. At least, that's how Parts
have always worked in the past
EDIT:
Note that i honestly dont even care at this point ^^'
Sorry. But im just so over it.
considering they took '16' as the ep count for first part, which is an abnormal number, they're making sure rules and formalities to not affect the quality, they are already flexible enough to give justice to adaption, so maybe they will go with whatever ep count they feel best, so not under 10, no way