Of course.

NGSA = Next Generation Single Aisle, the replacement aircraft for the 737 and A320.

Both the 737 and the A320 families are older designs. They've been updated over time and are still quite advanced (and sellable), but the technology has developed at a faster pace. The 787 is a game changer aircraft, meaning that it will change the way airlines operate (for the better), and, as such, will change hoew future aircraft are designed and manufactured (as well as how they are overhauled).

Many of those changes can be incorporated onto a single aisle platform and both Airbus and Boeing (as well as the engine manufacturers) are already in the planning phase for this new aircraft. Best estimate as of now is an entry into service around 2013, which really is not all that far away.

Airlines operating these new aicraft will have a significant operational advantage over those that do not. In an industry where every penny counts, this will be significant. If I were AA, I would not invest a lot of money right now into new single aisle aircraft or even re-engining the MD-80 as they will want this new aircraft as soon as possible.

737s are not going to replace the MD-80, the NGSA will. For this reason, I also doubt that AA will actually take delivery of the 737s they have defered. I expect that they will be converted into NGSA orders.