Will Apple ever offer Extreme Edition Intel CPUs in a MBP (or any other mac) or is the power draw too high and performance benefit too marginal to justify the increased cost?
No and No. The current Extreme Edition Sandy Bridge CPU's are all about marketing and only offer incremental benefits (and bragging rights, of course), unless you count the just-released Sandy Bridge-E (E=Enthusiast) CPU's, which are enormous in size and will never make it into any Mac.
Take the Late-2011 MBP "refresh": The Extreme Edition chip above the 2.4 (2760QM) and 2.5GHz (2860QM) quad Core i7's is the 2.7GHz 2960XM. You not only don't get any more L3 cache (over the 2860QM) and Intel might as well have called it a 2960QM, because it's also "only" a quad core chip.