I took that as a prediction of the future. In fact, it made me think that those beings might be the force ghosts for the Jedi we know behind the masks. So that was future Yoda ghost guiding himself how to become Yoda ghost.
That's a pretty interesting concept to consider. If being part of the living Force means that space and time basically have no meaning and one's conscious spirit can travel just about anywhere given enough skill then it's not outside the realm of possibility that post-ROTJ Spirit Yoda could be helping guide his younger self to ensure that certain events take place as they should.