I don't think it is official (yet), I have seen a story that Boeing is trying to convince HMG they can afford four. Recent press releases from Boeing UK and STS don't include a fleet number unlike some earlier ones. Speculation suggests no maintenance contract was put in place and the likely costs of it plus training are the issue. A side issue is that the E-3 OSD is 12 months before E-7 Entry into Service.
MoD seems to have been avoiding answering the question.
Written Question on 22 SEP 2020 reply 28 SEP 2020
[QUOTE
]Kevan Jones MP (Labour) (ex Defence Minister and Shadow Defence Minister), Member of the Defence & Intelligence and Security Committees
To ask the Secretary of State for Defence, what capability gap would be created for the Royal Air Force in the event that the order for five E-7 Wedgetail aircraft is reduced to three?
Jeremy Quin MP, Minister of State (MoD)
Reply
None. The E-7 Wedgetail is a step change in capability and reliability and meets the urgent need for an Airborne Early Warning and Control (AEW&C) capability as a critical enabler to UK military capability.
The transition from Sentry to E-7 Wedgetail will not result in any reduction in current capability.[/QUOTE]
If the existing capability is as f**ked as some have said then dragging Shacks and Gannets out of museums wouldn't represent a reduction in capability. Yes, I'm being facetious but 3 clapped out E-3s replaced by 3 new E-7s obviously wouldn't be a reduction in a capability which is severely degraded.