When teleporting into an unloaded chunk in 1.8, the player would fall while the chunk was loading, but be teleported back up by the game when the chunk loaded. This is not the case in the 1.9 snapshots.
1) check your Y coordinate
2) while not flying, type this command: tp ~1000 ~ ~
3) as the chunk loads, you will fall down
I expected to be teleported to my original Y coordinate like in 1.8.
Instead I spawned in the stone under the surface and suffocated.
This is much easier to reproduce on a server with high ping.