Funny, there's a hot rumour doing the rounds that the 400s are being returned to Airbus with a 'thanks, but no thanks' as they simply cannot fulfil their expected roles, particularly the para role...
Given the investment in the project, both by government & the RAF, I would consider that to be a little unlikely. Everything that can be done to make it work will be.....but an extension to the OSD of the C130J to cover the TAC & SF roles seems likely.