[Ibrîniðilpathânezel]

There are, to me, certain aspects of that dream which point to its source in the Higher Powers. Specifically, the foreknowledge that:

The Ring would be in Rivendell.

Counsels would be taken (possibly indicating a council would be held).

The Ring would be shown.

A halfling would step forth in significant way.

Gandalf never demonstrated any such degree of prophecy. Moreover, if he had known, I don't think he would have used — nor would he have been allowed to use — his abilities in such a way. This smacks much more of the Valar, and their behind the scenes activities, and Pronouncements of Doom, IMHO. They are much more the master chess players than anyone in Middle-earth, and the convenient timing of the dream, as well as the fact that it came to both brothers, thus helping ensure that one of them would go to Rivendell, seems to me a thing that they would do. Though I rather suspect they might've preferred Faramir as their messenger.