I can't imagine they will replace DMs at this point. DMs have been developed significantly in the last two years and there are a lot of notable advancements that have greatly improved their efficiency. Further, stable diffusion runs on DMs and that is already cemented as a pervasive open-source tool.

Further, it is also unclear at first how to add conditioning into this setup and how something like super resolution would work. Definitely not saying it's impossible, just that it is at a very nascent stage. It will be really cool to see how the two interact, such as incorporating DMs and PFGMs together in an Imagen-like setup!