Not that long.  I am unclear as to how the edge case blocks are selected and then disregarded in terms of how monero retargets difficulty, but after the first 144 blocks (at the most) we should definitely begin to see the difficulty go down.  We are 44 blocks of the way through that 144.  It may well start to head down sooner than that though, on the other hand, it may head up some more as well.  As I say I am unclear on how it determines which blocks are considered the edge case ones that don't get counted towards the next difficulty.  

At any rate, we should see the other side of the first 144 blocks within 24 hours and see a definite reduction in difficulty begin (if it hasn't started before that).  As heavyarms1912 says above, the full extent of what network difficulty will look like will take 720 blocks but once it starts going down, blocks should begin to be a lot faster again so hard to say how long it will take to get those 720.  I would guess that 48-60 hours would be long enough for us to see something like normalcy in terms of block time on the network again, although it could certainly be less time than that.