I do not know when the updated one is due, but...
If you log on to www.chambers.co.uk you can sign up for a news email. Hopefully in the future it may have some news about it.
Also, on that site, you can download the 500 missing words as a pdf.
OK, so I've now subscribed to their newsletter; the 500-word list I had already; and I resisted the temptation to suggest adding "to ferk/furk" & the adjective "leer/lear" to their new volume (both words my parents used in Sussex in the 1950s, meaning "look for" & "empty" feeling in the stomach). Seems we all now just have to wait & see. Thank you again for your advice!
GK I am surprised to find that leer/lear is not shown in Chambers 12th with the meaning you gave.
It was used by my family when someone was "feeling slightly unwell" relating to the stomach. We are from Wiltshire and Dorset
Quite often my Amazon orders come from Luxembourg (presumably for tax avoidance reasons). This doesn't affect the P&P - which I usually get free anyway, as my order is enough to qualify.