Can numeric version naming conventions for CiviCRM extensions use the Drupal module naming conventions?
It's hard to apply the Drupal model to CiviCRM because the release cycles are so very different. Drupal releases a complete overhaul every 3-5 years, with nothing but bugfixes in-between. Civi's release cycle is more frequent and incremental, with some big changes in each major release but a lot of stability too. Drupal intentionally breaks compatibility with all modules with every new major version, whereas it's not uncommon for a single copy of a CiviCRM extension to work equally well with 4.4, 4.5, 4.6 &amp; 4.7. For this sort of thing, the Drupal versioning convention would be too rigid.

Currently each release of an extension explicitly declares which version(s) of Civi it is compatible with in its info.xml. You can see this at a glance by looking at the extension's page on CiviCRM.org - each release has one or more compatible versions listed.

The only downside I've seen is that often times extensions continue to work fine with a new version of Civi but their info.xml hasn't been updated to show it. E.g. once 4.7 is released, the majority of 4.6-branded extensions will probably work fine, but you won't be able to automatically download them until someone manually tests, verifies, and bugs the maintainer to update their info.