From emerge: WARNING: One or more updates have been skipped due to a dependency conflict: x11-base/xorg-server:0 (x11-base/xorg-server-1.14.3::gentoo, ebuild scheduled for merge) conflicts with <x11-base/xorg-server-1.13.99 required by (x11-drivers/xf86-video-mga-1.6.2::gentoo, installed)
We have received reports of problems when using xf86-video-mga with recent xorg-server. If you say that it works for you, then we can relax the dependency and allow xf86-video-mga and xorg-server-1.14 to be installed at the same time.
It would be ok for me to close this bug as WONTFIX, then. For the system with the MGA card X11 server support is not a top priority, and I can't test the combination xf86-video-mga & xorg-server-1.14 there right now.
How about removing mga from the default VIDEO_CARDS?
I have removed the versioned dependency.