If you have an unreversible mixer, congratulations. Bitcoin will almost certainly want to adopt it. However, it won't fix fungibility.
When you say that, are you referring to Bitcoin 3rd party development like Dark Wallet? Or the core dev team? I don't think the core dev team would ever implement that tech in to Bitcoin even if it was perfect.
Why would they not want to adopt it? We're talking about Bitcoin as in the open source beta phase project.