I think the situation is going to completely explode in the near future. Things are way too unstable as long as Eri knows and Harima and Tenma don't. My theory (of which maybe 10% might actually happen :P) is that the oyster date will fail spectacularly due to the Tenma factor, leading to Eri shouting out the truth to Tenma, a dramatic confession by Harima, a rejection (or at least an apparent one) by an overwhelmed Tenma, and a guilty Eri picking up the pieces of Harima's heart. When the dust clears, Harima and Eri will be going out and Tenma will - somehow - be with Tougou (a confession mistaking Tougou for Karasuma would have an ironic touch), which will greatly complicate the making of the album movie. Eri and Harima will try to make it work but fail because of Harima's still strong feelings for Tenma and Eri's jealousy, while Tenma, who is finally aware that Harima liked her from the beginning, falls for him. Then, at the end of March, Shawn returns and the final battle begins.