None of the RAW formats are open and they contain lots of information which only the manufacturers know about. In fact there are so many different RAW formats that the open source RAW convertor
DCRaw currently supports over 377 different formats.
There are differing opinions on this but, personally, I don’t think DNG is the answer. It is not a true open standard because it doesn’t document all the essential information in proprietary RAW files, only that which Adobe can work out.
Lots of data in proprietary RAW files is/may be encrypted. For example, Sony encrypted the RAW files on it’s F828 camera in 2003 and when Nikon released the D2X in 2005 it encrypted its white balance data within the RAW files. They weren’t the first or last companies to do this. It's done to stop other camera manufacturers unravelling their proprietary systems.
So if there is information in your .CR2 file that Adobe don’t understand or can’t decode (usually EXIF data, or encrypted data or other things) it won’t be in the .DNG file.
In the long run, there isn’t an answer to this problem. DNG works OK but if Adobe disappear then so does DNG. PSD is a good storage format, it supports layers and it’s lossless which is a huge advantage, but again, if Adobe fall so does PSD.
Many people argue the best long term solution is TIFF. But TIFF has it’s own technical issues, aside from being harder to implement, including a maximum file size of 2GB and no UNICODE support.