From Reddit: NO level sync when entering a dungeon with less that required players!

[ShoeVsYou]

Last i read about it, current lvl50 and 51-59 dungeons will be part of the high lvl roulette

This is incorrect. They have specifically states that lvl50 dungeons will remain in High Level Roulette, while 51-59 dungeons will be added to the Low Level (or leveling) Roulette.