Software companies do this all the time too, for reasons that baffle me (so it must be some idiotic marketing thing). Macromedia went from releasing Dreamweaver 4 and Flash 5 to Macromedia Suite MX. Um. OK. Then it was MX 2? Then Adobe bought Macromedia, and renamed all of their products Creative Suite. Then CS 2. Now I think they are on CS 5 or 6. Why? What is wrong with Photoshop 14? Is it that hard? Someone in class a couple years ago said she'd bought photoshop 4, and both the instructor and I gaped at her. She meant CS4. Yeah, slight difference there. Like about 10 years of software development.
Remember when we had Windows 3.11, then Win 95, then Windows 2000 and Windows ME, then Windows XP followed by Windows Vista? Did that make any sense at all? NO. Now we have Windows 7 and Windows 8. Where did these names/numbers come from?
So, if WotC has any brains left at all, it will be AD&D 5th edition. Stick with the sane and stable naming convention. Be logical. For once.