Edit: As reported by Rorate, and the "Resistance" among other, there will be a meeting between Bishop Fellay and Cardinal Muller. Since then we found this update by Katholisches:
[Update 17:00] The meeting between Cardinal and Bishop Fellay Müller has now been confirmed by Vatican spokesman Father Federico Lombardi. It has already been reported by Vatican Radio. Curiously, the message category was assigned "ecumenism" on the website of the Vatican radio station.