Can they at least switch the decals?
As a graphic designer, it would depend on whether the budget is available to produce the detailed artwork for the new graphics and probably printing the new vinyl wraps.
Even though the basic concept has been created, the detailed design work to create the large graphic panels, taking into to account the various multi surfaces and compound curves is quite a detailed and exactling process, so this would have to be budgeted for.
The graphics for such a project would normally all be batched produced as it’s far more economical to print, output and kiss-cut the necessary graphics for all of the project in one run and then hold this in stock.
So yes, the new livery could be applied going forward, but it would probably incur considerable extra expense for which a new budget would have to be found and would most likely double the materials and production costs for the remaining units to be done.