My point is that it's not inherent in the notion of a browser that enterprises have to upgrade. IE is simply the existence proof.
There's a conflation here, by enterprise, between browser-as-client for in-house apps and browser-as-web-browser. If your test for degradation is that the in-house apps continue to work then sure, that's verifiable. But if you acknowledge that the same program is used for both purposes then you would find it much harder to show that no degradation of user experience and productivity have occurred.
While most in the tech industry will not agree with me on this, but the inability to browse the general web would not be that grave of a detriment on the productivity of the enterprise.
I personally think the success or failure of the rolling release model with separate streams for early adopters depends entirely on the QA standards of the vendor.
This is necessary, but not sufficient. Another big thing they need to do is to not break code, even if intentional. Probably the bigget thing they can do here is to not introduce "experimental" features, and then tweak them over time. The way a lot of devs work, whether you like it or not, is to find a feature from the web that solves their problem, put it in their code and test it on their current browser. If it works then they're happy. Three months later when that feature changes, because the feature isn't finalized anyways, you now have a bunch of apps this guy wrote that just broke.