10.02am Monday, February 28th. The first East London Line train arrives at Highbury and Islington Station.
The final stage of the extension is opening exactly as predicted back in January. Board at 9.28am for a direct train from Brockley. Here is the confirmation from TfL.
All ELL trains thereafter appear to run to Highbury & Islington, according to the TfL journey planner, which is also in line with recent information, but we haven't confirmed this yet and it's possible that some may continue to terminate at Dalston.
Oh East London Line, we love you.
Thanks to IanVisits for the info.