Was any of that really unexpected? That Rebecca was the mother was obvious since we found out Annie Hobbs wasn't. I'm not surprised Rebecca has a photo of Alec at Dereks murder, cause I think she is the note sender. I don't believe Alec killed him though for some reason.. I think mother dearest did that. She is getting a late come revenge on Alec (and Ted?). The Thayer thing was pretty obvious as well. The only think that suprised me was that Sutton was in on it. The Sutton character is really becoming very one-dimensional and evil, and rather unrealistic!
My guess for next season (or the story as a whole) is that: Rebecca got pregnant during her affair in LA. She called to tell him this during his operation on Justins mother. Alec bullies her in to giving the babies up. Possibly the idea was that Ted would get one daughter, and Rebecca the other (when Sutton and Thayer where in Beverly Hills they never met the wife), but Annie Hobbs, who had been in the same hospital for the birth, got in the way. Alec bullies her to accept that her baby was lost and leave Ted and his family alone. (this would however also make for a rather undimensional story - why would Ted accept never knowing what happened to Emma - provided he knows she existed). Well well... these are my bets - let's see how it pans out!