I still have my first 35mm film body: EOS 620. Paid a lot for it at the time, and now it isn't worth much, so I just keep it. I have not shot film for a long time, and have been thinking about it again.
My first digital was a Canon G2. I still have it for pretty much the same reasons as above. Having it converted to IR has crossed my mind. I replaced the G2 with an Olympus Stylus that is water, dust and shock proof.
I also have a Nikon EM that belongs to my mom with a 50mm f1.8 lens on it. This camera does not work, I tried a new battery. Not worth fixing (I think) and can't bring myself to toss it.
As far as the new DSLR, I'm not sure what I would do with it. Depending on the replacement product cycle, residual value and desire to upgrade, that would determine sell or keep. The 7D makes fine pictures as does the 5DII. It would take a lot to upgrade just to upgrade. Both current models do more than I know how to use. I could fill up 32GB flash cards and keep buying new ones for less money than getting film developed- even at maximum size RAW+JPEG.
At current projected prices, I would have to sell the 5DII and add about $4k for the 1Dx, which is the next step from a 5DII unless the 5DIII is something extraordinary. Same numbers to go from a 5DII to a 1DsIII, which in some ways is a downgrade. Out of my budget for a camera. I would rather spend the $4k on lenses.