Web Analytics has since early 2010 seen a notable decline in both use as a description of Internet traffic analytics as well as in the Google searches.
While both have many times been used as synonyms, Digital Analytics in fact covers a wider range of data sources where Web Analytics data is a subset.
From my perspective the shift came when Comscore bought Nedstat in an effort to move into the web analytics space and the release in 2011 of the Digital Analytix analytical tool (a.k.a. Report Builder previously). The ability of integration of additional data sources to extend the dataset meant a leap into Digital Analytics.
Another indication of this shift was when the Web Analytics Association (WAA) morphed into the Digital Analytics Association(DAA), WAA officially became DAA in March 2012.
When Web Analytics Demystified in 2015 become just Analytics Demystified it was obvious that the full circle had been completed.
"As more digital data streams became available, the responsibilities of the analyst broadened and the term "web analytics" became known as the study of data collected exclusively on websites."
Given the current speed of increased search volumes Digital Analytics is expected to surpass Web Analytics as a search term mid 2018.