There have been rumours that Trixie is leaving #CallTheMidwife, but the fact that they made such a big pointy point of setting her up to be a partner in the Lady Emily clinic makes me think they intend to do something with that.
If she was leaving, they could have said nothing, or sent her back to New York, or given her some nondescript job, or had her be full-time Lady Aylward, or had her *just* work at the Lady Emily.
The highly specific role of partner makes me think there's a plan