Tl;DR: 13.0 profiles will be removed some time soon unless there are enough reports broken on 13.0->17.0 switch.
13.0 profiles been a while in Gentoo tree and are already deprecated on some arches but not everywhere. If you have problems using 17.0 profiles as a default please file a bug and pile it against against the tracker bug (fresh one): https://bugs.gentoo.org/672960 Feel free to add toolchain@ and me (slyfox@) to CC for all obscure bugs you see as those are probably related to toolchain defaults changes. There is no defined timeline for removal yet as the breakage scope is not clear. But to pick an arbitrary point in time to get order-of-magnitude: in about 3 months 13.0 profiles will be gone (spring cleaning time). -- Sergei