A while ago I compiled statistics of the versions of Google Earth in use in the wild (well technically accessing network links at nearby.org.uk) – well an updated version is now available.
For comparison here is the version from last Sept.
Conclusion: GE3 is definitely on the way out, but still actively used. A large number of people haven’t updated their GE4 for a while, and there might be a new version coming out sometime soon.
Update: It turns out my simplistic test for useragents beginning with kh_ missed off Mac and Linux clients – so here is a another updated version that does include such clients. Thanks to a commenter on Gearthblog for spotting this!
(I could rerun the above reports but see little point)
Update 2: It seems the new version was incorrectly calculating the total for Mac/Linux users – updated the link in the update above to correct this.