I have yet to rebase my old armies....and I do not intend to do so.
Over the past months I have really enjoyed Age of Sigmar. The Campaigns, Narratives, Fluff, and all the new hobby abound have filled my time. I have seen many people rebase their old armies to the new round bases and it is great seeing people embrace this new system, but I simply could not bring myself to rebase (even my unpainted models) despite them looking much better on rounds.