The amount of sleep turns is determined by RNG, and the lowest is 2 turns, so of Breloom is slower, you are gaurenteed a free turn. If you're faster, the turn you put them to sleep counts, so you could possibly not have a free turn, the same way as in Gen 4.
The change is when you switch. In gen 4, if you were RNG'd 3 sleep turns, yet switched out after 2, when you come back it will continue. In gen 5, the RNG is done again, and you have anywhere from EDIT: apparently, its 1-4 sleep turns once again.