Very little is known about Thief 4 as Eidos and Square Enix have kept quiet, but the rumors of Thief 4 have been strong and frequent. At least fans know to expect third-person views in the game, at least during archery.
The posted image of the playtest at Eidos Montreal was spotted by JeuxVideo(translated) where they mention a mixture of the third-person view is used when Garrett is travelling, climbing and using archery. This image at least proves it true for archery.
[StrategyInformer]