If you actually read the easyJet press release carefully, it talks about "proposals to reduce the operation at Luton" and in the notes to Editors section at the bottom there is a further comment that there are no changes to the Luton program.
Personally, I read this as they actually haven't decided to do anything at LTN: this is just a warning shot to the LTN management to play ball or they will reduce capacity; announced on the same day as the EMA base closure to give it more weight. I am guessing that they fully expect LTN airport to give them what they want and there will actually NOT be any withdrawal of aircraft.
Alternatively, I can concede that it may be the case that the full LTN winter program has not yet been released for sale (would be rather odd if true) which could explain the reason why withdrawing three aircraft would not result in any changes to the current program available for public sale.