The next direct-to-DVD and blue-ray special confirmed for 2013 is titled 'King of the Railway'.
Though nothing is yet known about this new special, the only clear evidence is a book that will be released in 2013 that tells the story of the new movie. The other fascinating thing about this movie, is the strange locomotive behind Thomas, that seems to be based on and represents Stephenson's Rocket.
One can only assume that this is prior to the release of Season 17, which will have a new series writer and new animation format which has moved to Arc Productions, there is also talk of bringing back several original characters from past series, but this is yet to be confirmed.