It's kind of sad that new stuff sometimes makes us question existing gear beyond where it makes sense to do so.
If the 5D does it for you, keep shooting and enjoying it. It has not suddenly become a poor camera at all. It is capable of awesome results. In a year or so, 2nd hand ones will be available, and the price of new may be down too.
I bought my 20D in 2005. I still use it. great camera for my purposes. As my technique and preferred subject matter has have evolved, so have some of my needs. I wanted FF, so I recently grabbed an open box 5D. It offers the possibility of great results at a great price. that's what matters to me.