Otto replaces Vagrant for the common use case: if you're just a person who wants to run a personal dev server, they'd like you to move onto Otto.
However, Otto is just a layer on top of Vagrant that automates a lot of the decisions that a dev would usually make. Vagrant is still relevant for other use cases, so they'll continue to develop it as a standalone product, too.
> Vagrant is a mature, healthy project that is continuing to grow every day. We are committed to supporting Vagrant for the foreseeable future and will continue to release new versions. Otto is our vision for the next generation and will be developed alongside Vagrant.
However, Otto is just a layer on top of Vagrant that automates a lot of the decisions that a dev would usually make. Vagrant is still relevant for other use cases, so they'll continue to develop it as a standalone product, too.