Currently, 17W is the lowest thermal design power offered by Intel's Ivy Bridge CPU line, although a software tool can lower the TDP to 13W. Still, the next step is what everyone is looking forward to.
All of them will be designed on the 22nm manufacturing process technology, but will only be available in limited quantities.
Since Haswell units are on the way, the 10W Ivy Bridge chips are just there, or will be, to fill the time gap.
On that note, while Haswell has a more advanced architecture to draw on, Ivy Bridge is still the same, regardless of optimizations.
As such, it is possible that 10W the Core Series chips will have to settle for a lower performance.