Were on block #33217ish. With 2400 blocks per difficulty change.
33217/2400 = 13.84 (means 13 difficulty changes, were 84% of the way through #13)
2400-(.84*2400)= 384 blocks left till difficulty change.
2.5 mins per block target = 960 mins or 16 hours. This is assuming the target time is matched, which I am not sure is true or not. I would guess around that amount of time from this post.
I know its a factor of the target block time (2.5 mins for PXC) and whether blocks are solved on average faster or slower than that time. However, I do not know the exact calculation to get a current estimate. If anyone knows, I would be enjoy learning.