We won't ever have level selection available, simply because many things (your choices, the enemies you do/don't kill, your behavior in the level) affects events in future levels, and if the game doesn't have that input from the prior level, some cutscenes will break/won't work, because it's expecting you played through the previous level.
If enough people REALLY want it, we might possibly do it in a future update, but it'd take some work to add in extra variants/checks for things in regards to players deliberately having not played the earlier levels.