The (CR2) format isn't much changed, it's the new info that's the problem. Unless the app has been programmed to understand the sensor characteristics (and a profile or 6 developed for it...), and whether special lens correction handling is needed..., Photoshop/ACR just won't touch it.
I mean, you can change the model & make using exiftool and ACR will probably (may anyway) read it, it just (probably) won't convert it properly...
There is a huge misundertanding which prevails in the photo community: CR2 & NEF and most other formats are not rocket science to reverse engineer (and don't change much, from year to year, and model to model...). Most are tiff based, but the data in them is proprietary and the sensors all have different response characteristics, and a little to a lot of human effort is required to implement support for them in ACR, thus the reason that:
* Adobe likes to get money for their efforts to support new cameras.
* You can't convert a new raw file with an old dng converter and expect it to work (either).
* Canon's DPP (and Nikon's NX2...) also need to be upgraded to convert raws from new camera models.
Could it be to make us spend more money on things we already have. £70 for the pleasure.
Well, you could have downloaded the free DNG Converter and converted the raw files to DNG that WOULD have been supported your new 6D camera...oh, did I mention that DNG Converter is a free download? Yes, I guess I did :~)