P&O have always gone to great efforts to update public areas, but in terms of soft furnishings in cabins, these tend to be updated as a very last resort.
They have operated a fleet of similar ships previously, which Pearl, Dawn and Jewel all being very similar, so I don’t doubt they could/would put Grand with Pacific Adventure and Pacific Encounter (ex- Golden and Star Princesses).
I know pax on the 3 day comedy cruise (following my parent’s cruise) were emailed 48 hours prior to departure and told that the ship wouldn’t be sailing for a lot of their time “at sea”. She was set to anchor so that work could be done on the hull. I’m uncertain what sort of work would be done, but perhaps she’s really not in good shape, and not just cosmetically. Mind you, if it were in really terrible shape, they should be cancelling cruises and putting her in to dry dock.
At any rate, as I said, it wouldn’t surprise me in the least if this news was more than a rumour.