I think the next fall of difficulty is coming in September. But it will last even lesser than the 4-5 window period last time. The price will decrease after that period a lot if the experiences of last time were anything to go by.
Price will fall exactly at the end of 21th of August. How do I know?
Two new snapshots have been announced for that day,
https://bitcointalk.org/index.php?topic=675455.msg8270526#msg8270526
Not much PTS left for sale compared with last time a snapshot was announced. People are pulling theirs off the exchanges early this time around!