Absolutely. But I'd imagine they'd go one of a few ways:
1) The meter will fall back to 2G (until thats also retired - but long enough to meet out the contract - I doubt there are any units in service which cannot fall back to 2G)
2) The comms unit will be swapped out
3) The comms unit is already do 4G hardware wise, and will be patched OTA. (Signal permitting)
4) O2 end up delaying switch off in England & Wales, at a minimum. (3G switch-off could still occur in Scotland) - though would add 3 years to their switch off timeframe.
5) The meter goes back to a traditional "dumb" meter from a supplier POV (back to meter readings) - only with an IHD, and those customers get added to the chunk of customers who need updates/upgrades/SMETS1 swapouts etc.
2.25 is the key bit - but they very much gloss over the issue (isn't really their issue, yet)
DCC won the contract in 2013, for 12 years. (2025)
(You can view their license here ->
https://www.smartdcc.co.uk/about-dcc/governance-regulations/smart-dcc-licence-regulation/ but it's a hella long wordy snoozefest)
VMO2 3G Off estimate (2025) seems very coincidental to me
Without the wording on the contract, I can only speculate - but I'd imagine O2 would have been very careful with how it was spec'd in the contract - they'd lose out if they ended up with long term service outages, for example. I simply can't see an MNO of their size making the mistake of saying they'd be providing 3G only infrastructure.
DCC Have just signed a contract with Voda for 4G service (
https://www.ispreview.co.uk/index.p...grade-energy-smart-meters-with-4g-mobile.html - note in their announcement "up to" 15 years

) - so they'll be running parallel and migrating over (Sounds good... SMETS1 migrations to work again post energy supplier change is going really well....

)
It will be interesting to see how other 3G switch-offs go, if speculation is correct and Vodafone have already seen issues removing 3G - VMO2 are pretty screwed