I have renamed migrate.module as migrate, and merged migrate-module with it. The reason I kept migrate.module (after renaming it) is that it had already a tag wiki.
The reason there was entity-module (which I renamed entity-api-module) is because the entity API is a part of Drupal, and there is a third-party module that is the Entity API module. There was the need to have a tag for that third-party module, and for questions about the Drupal entity API; that is why there is entity-api-module, and entity-api. Notice that Drupal 8 has the Entity module; questions for this module should be tagged entity-api.
If Views becomes part of Drupal 8, we will have a similar problem. Probably we should have views-module for the third-party module, and views for the Drupal core part. That is in the case the Views module becomes part of Drupal 8, and it doesn't change name during that operation. Code of the CCK module was incorporated in Drupal 7, but as part of modules such as the Field module, the Field UI module, the Text module, and the Number module.
Generally speaking, there is no need to include .module, or -module in a tag. It is done when it is not differently possible to disambiguate two tags that would differently be the same.