Eventually, gcc will be updated. Funtoo just tends to be conservative with the toolchain since Funtoo's primary focus is on servers. Still, I agree that I'd like to see newer toolchain packages available for those who want them, such as developers. In any case, you can write/modify ebuilds yourself or even use Gentoo's ebuilds. You can also use the toolchain overlay if you wish. There could be potential issues, but I've personally not run into any. In any case, I've written a Funtoo-style, self-contained gcc 5.3.0 ebuild for my own use which I can share. Iit's based on Funtoo's gcc-4.9.3-r1, so it doesn't apply the plethora of Gentoo patches and, as a result, probably won't work properly on a hardened system. I did try using 4.9.3-r2 as a base (for compatibility with hardened), but I ran into a mysterious bug resulting in failure to apply all of the Gentoo patchset.