Alexis and Martha only in the opening scene I hope is not a sign of things to come, .
I wouldn't infer too much from one episode, especially this one. They had a lot of ground to cover here, including the aftermath of Castle and Beckett getting together, Beckett's resignation from the force, the truth behind the conspiracy, etc. Not sure where they could have squeezed in more of Alexis and Martha . . . .
Not that all that season cliffhanger stuff has been dealt with (for now), they may have a little more breathing room.