I'm actually not too sure, the /var/db reference has automake:1.14 and re-emerging will cause it to have 1.15, but it doesn't directly reference it ... So this one may actually be more complicated than a revbump, but it isn't playing nice with --dynamic-deps=n.
I'm getting like an endless stream of packages that keep wanting me to install automake:1.14 that end up not wanting it anymore after re-emerging :P Well, at least sdl-sound and dev-python/pygtk-2.24.0-r4:2 so far ... I also have x11-proto/resourceproto-1.2.0 wanting an older version (so even older bad cache)
Please explain the problem and then the solution in clear terms.
Use --changed-deps=y as a workaround. A news item about the problem will be released soonish.