Just out of curiosity, why do you think WebKit2 is the "standard"? Just because they named it "WebKit2"? Had Google named their multi-process version "WebKitB" would it be equally standard? It certainly came FIRST (I think it took WebKit2 years before it had an answer).
I think this is a success of open source. Was the creation of WebKit a failure of Mozilla open source? Of course not. Sometimes you need to just actually test two ideas instead of discussing them.
EDIT: Upon further inspection, I think current Safari isn't even using WebKit2. The wiki still says it should be considered a "technology demo", and exists largely in parallel to WebKit. So whatever multi-process thing its doing now I guess is separate? It's not clear to me.
EDIT 2: I guess it is using WebKit2, so my criticisms stand.