OK, wow. Now you really have me confused. If there hasn't been a decent upgrade since the 20D, what are we even discussing?
Moving from APS-C to FF isn't an upgrade so much as it is a change of format. It would be like changing from using a FF to MFDB, except that some of your lenses may still work.
The 6D and the 5DIII aren't decent upgrades to the 5D2 and the 5D2 wasn't a decent upgrade to the 20D. It sounds like the entire Canon lineup since the 20D has been a huge waste of time.
From the 20D to the 30D, there was no change in IQ, some even argued it got worse. The screen on the back changed and that was it. The 40D was marginally better than the 20D with a few extra megapixels thrown in. The 50D delivered IQ that was still measured to be about the same as the 20D plus a few extra megapixels on top of the 40D. Whilst the 50D can now shoot at ISO 12800, nobody really does because you can't recognise anything above ISO 3200. The 60D gave us even more MP but still the IQ hasn't gone anywhere and wasn't really that different to the 50D.
And yes, a lot of people are sick of Canon offering something almost the same as what the new camera replaces except something a little better.