I'd still be using the Rebel series if the 6D weren't released. I consider myself somewhat experienced and have invested well over $1k in glass. For my purposes, there's simply no way to justify the price of the 7D, and even the xxD series is highly questionable. It's the exact same sensor, and AF doesn't really matter to me, beyond having a functioning center point available if needed. A lot of the other extra bells and whistles strike me more as marketing than anything particularly useful to the pursuit of making good images. With exceptions for certain niche cases, of course.
No one should feel like they "need" to upgrade beyond the Rebel series if they aren't doing a lot of action work that relies heavily on AF. I know of a full-time pro who also used Rebels exclusively for quite a few years until the 6D dropped. (I guess some might consider the 6D to be the "Rebel of FF" -- a good thing, in my eyes!).