Not sure if a 50% jump would be within the rules of the Bitcoin Network, because those 2016 (2015) blocks would just breeze through.
This value looks a bit high: http://blockexplorer.com/q/estimate
How about Next difficulty (estimate): 285,052,471 (+6%)
http://bitcoindifficulty.com/
The network allows up to a 300% increase (and a 75% decline) per adjustment. A max difficulty jump has happened a few times at the start of the "GPU era". I doubt we will ever see a 400% increase again because the network is so large now. With the network at 3 PH/s it would need to increase by 9 PH/s within one difficulty adjustment. Due to timing it probably would need to be be more like 12 to 18 PH being deployed within a week. That would be like shipping 6,000 BabyJets or KNC Jupiter's every day.