Well I can't explain the next diff jump. I mean every ASIC on the market ROIs very very hard. Even S1. So who keeps adding power?
Might be ASIC companies that couldn't sell their gear like Spoondolies. Maybe even Black Arrow started mining with their X3. Some S2 were sold, some S1 and some SP-10 but they don't account for the upcoming 14-18% jump.
asicminer chips are just now getting out into the wild - its likely some of these companies are premining with the chips and/or building private farms before they focus on public sales (hashratio.com for example, which seems to have mimicked the S1 design, but can probably achieve 300-400GH in the same power/footprint