Eh, as a researcher at the periphery of the Human Microbiome Project and American Gut project this has been the accepted (and already shown, experimentally) conclusion for quite some time.
Those aren't particularly new things to study. We have tons of murine data on the subject and quite a few PhD students over the last 4-6 years have done their PhDs on microbiota and diet with themselves as the guinea pig, so to speak (2-4 year longitudinals).
There are a couple mouse papers out that don't directly address the issue in 2, but that permanence (or lack thereof) played prominent roles in their findings.
1. The speed at which the microbiome can change (<3 days)
2. The permanence of such changes (some of them are more permanent than others)