Will the language incubator allow the addition of "English for native speakers", "Spanish for native speakers", etc. for people who want to improve their native language skills?
This would also have the effect of improving translations, so it would be in Duolingo's self-interest to allow this.
Even now, there are users that are taking the course of their native language. I myself am taking the courses of some languages that I already speak fluently as there always is something to review and to practice since I'm not native in those.