Comment 12 for bug 848154

The reason for not switching to v7 in jaunty already was that it took more than one release to sort out all issues and build failures for a clean v7 build with all planned optimizations that were agreed with ARM to end up in ubuntu.
The ubuntu arm port would have been v7 from day one if that would have been possible, but as it happened, jaunty was just a plain rebuild of debians armel, for karmic the switch to v6 (and a lot of other bits like thumb2) was made, v5 was never a target architecture for ubuntu.
These bits were discussed at the various UDS's, feel free to search blueprints.launchpad.net for the related blueprints.