Paul M
I believe there was a plan to retrofit the Vigilant with a 'more' glass cockpit. I assume this will now be dropped if the aircraft is retired.
As for retrofitting the Viking I think it will be neither sensible nor technically practical. However that does not mean they (Contractors and Project Sponsor) won't waste large amounts of cash and man-hours doing it (trying) before admitting it's not worth pursuing.
In a world of shrinking defence budgets the Defence companies are even looking to wring a few £ out of areas where previously there was not really any budget or interest in doing it. I expect that the glass retrofit feasibility study would have a budget of a least £75K to start..................... not a lot of cash in defence terms but hey...............
Arc