The Internet Archive, incidentally, already seems to maintain copies of Wikimedia projects. I don't know to what degree of fidelity. Additionally, the WMF's core deliverable is already to provide and sustain access to its projects. It has an endowment for that purpose already. Other websites and media that might have ephemeral access due to their nature as short-term tools need the IA to be preserved, but the WMF's projects seem to occupy a different space. It's sort of like asking if the Library of Congress needs to invest in some external project to preserve and organize its collections. No, that is its actual raison d'etre.