2.7 has an up-to-date backport of the C IO lib (as well as the memoryview object), which means it is better for people wanting to ease transition to 3.x.
But of course, as Martin said, few people will want to support 2.7 only and not 2.6.
Since 2.7 will be closer to 3.2 than 2.6, the result will more likely be: many people will want to support 2.7 and 3.x - which is really what we should be after.
Supporting 2.7 doesn't mean that you have to use the nonlocal keyword (nor does support for 3.2 require that keyword). So I'm not sure how the backport of a feature to 2.x could encourage people to forward-port to 3.x.