There has been quite some speculation what this may or may not involve and the transition from the previous programme which made use of the word enhance to this one, which describes an extension, should make it fairly clear what the scope is.
From the contracts journal
The UK Ministry of Defence (MOD) Armoured Vehicles Programme (AVP) has a possible future requirement to deliver a Category A Challenger 2 Life Extension Project (CR2 LEP). The user requires the Challenger 2 Main Battle Tank Out of Service Date extended from 2025 to 2035 in order to continue to provide precision direct fire manoeuvre capability across a broad spectrum of operations.
The MOD AVP is conducting a Market Survey to inform the CR2 LEP Procurement Strategy and Initial Gate Business Case.
That is it, extend the life from 2025 to 2035, and that is a ‘possible’ as well.