There was an article in today's New York Times saying May 24, 2022 is the opening.
I'm not sure which stations will be served right away.

From the Times:
"Heathrow Airport has had a subway link for decades. When the Elizabeth line’s next phase is opened in the fall, passengers will be able to travel from Heathrow to the banks at Canary Wharf in East London in 40 minutes; that is a prime selling point for a city desperate to hold on to its status as financial mecca after Brexit. All told, the line has 10 entirely new stations, 42 miles of tunnels and crosses under the Thames three times."

That will be nice for visitors!

ETA--After I wrote the above, I saw the 2018 thread about it. Maybe someone else can describe all the delays! Won't someone please invent the Transporter?!

Worth looking on YouTube to see some of the difficulties in tunneling through graveyards and beneath ancient buildings, slotting stations in between churches and finally getting the signalling working for what is not a tube, it is a whole rail system with full size trains.

Part of the difficulty has been that in full through running the trains will have to work seamlessly with different signalling and control systems at each end, and fit into the schedules of other trains running at the outer ends. After the over-optimism of the earlier plans, they've been ultra-cautious with lots and lots of testing, and now a staged introduction of services, so that passengers on the outer ends will have to change at Paddington and Liverpool Street until they're sure it's OK to run through. Plus there's some extended problem at Bond Street, which won't be served by the new line for a few months.

https://tfl.gov.uk/travel-informatio...elizabeth-line

there was a tv series done on the work .It was most interesting

Fitting Bond Street station into the tiny space left in some of the most expensive pieces of land in the world has been almost like doing Origami inside a bottle but using marble, steel and concrete.

Her Maj turned up today to open it, and was given an Oyster Card for her trouble.
Will be useful when it is all joined up later in the year (maybe).

We see Her Royal Majesty @ the Elizabeth Line opening.
HRM (whispers to her personal assistant): "Now that this is finally over with, I want you to rush me over to the Hendrix Museum. Forthwith, if you please."
Assistant (brief pause): "W-why yes ma'am, right away ma'am."
(snaps finger to summon the driver over)

I am done. the London transit