Looks like TFL have updated their information. They are now saying 30 March, which is Good Friday. We'll see.

https://tfl.gov.uk/bus/status/?input=122...n=outbound

DARTMOUTH ROAD / LONDON ROAD, SE26: Routes 122, 176 and 197 are on diversion until 30 March due to works at Dartmouth Road, SE26. Route 122 diverted via London Road, Sydenham Rise, Sydenham Hill and Kirkdale both ways. Routes 176 and 197 unable to serve Forest Hill Station and diverted via Sydenham Hill and Kirkdale both ways.