Byrne's MOS revamp hasn't been "tossed out," as much as it has been completely replaced with the new
Birthright origin - although DC is pretty much skirting the issue as to what his current origin is - as seen in
Superman 650, the implication is that it's not that important.
All-Star Superman isn't really the Silver or Bronze Age Superman per se - more of a "no crisis" interpretation of the character. I believe that Grant Morrison has described it as a what-if-crisis-never-happened type scenario. However, just like in the pre-Crisis comics, Superman
has gone through continuity changes, we just don't know what they all were. The end result being that you've got pre- and post-crisis continuity elements combined. But the character himself is very Bronze Age, very definitive.