I saw that at RealGM the other day. Leading up to the draft, OKC was very interested in Beal and there were rumors they might make a play for him, with Cleveland I believe involved in the discussions. He would have been a perfect fit with the Thunder because of his ability to space the floor for Westbrook, his defensive ability at either guard spot, and his attitude.
I highly doubt there were serious trade talks regarding Harden, though. At the time they were fresh off the finals loss and still thinking contract negotiations. There might have been exploratory talks, but little more than that.