Someone once said “If it ain’t broke, don’t fix it”.
If VS continues to win awards with its current Upper Class Suite, then I would imagine that is hardly an incentive to switch away from it.
Remember they already had a duff investment in their J2000 wedgie bed, which was removed from service.
Changing a seat/refurbishing a cabin is a major investment, and Virgin (as is the case with almost all airlines right now) is hardly awash with cash.
They *have* spent money re-designing Premium Economy, which is now one of the leaders in this class.
I would imagine Economy seats will be the next area of focus, and this will probably have to wait until new aircraft come online.
UCS can get a little passe (check out the “Austin Powers-esque” diamante trim) and the seat shells are susceptible to chips, but the cabin is far from tatty on my last A340 flight with Virgin Atlantic just four weeks ago I had no major complaints in terms of the cabin needing a refurb.