Intel is on a mission to reduce the power consumption of its x86-based chips. Intel has done this through continual die-shrinks, new architectures, and the Atom processor line. The upcoming Haswell architecture is said to drop power consumption to under 10 watts, as measured by the TDP, but that isn't soon enough for tablet makers.
Intel wants to get their chips into all of the new Windows 8 tablets, but the current Ivy Bridge architecture bottoms out at 17 watts, a bit hot and battery hungry for most tablets. The Surface Pro is a rare exception and is using one of these Ivy Bridge ULV processors, but will have battery life more similar to a laptop than a tablet.
An industry insider is saying that a future Ivy Bridge revision will reduce power consumption, though the exact consumption numbers were not discussed. It's not clear when this new revision of silicon would come, but one thing is for sure, you shouldn't expect it before the end of the year.