CaMeRon has way for this . It was used when new theme was developing for e107.org. I think it has something related with user theme setting. If I logged in, then I saw new theme, but other visitor saw old theme. If I remember correctly, there was condition to use the same name layouts for old and new themes. But I don't know details, so yes, it's possible but you need to ask maybe on github or gitter. Only CaMeRon knows answer.