Big Finish will be releasing a Third Doctor Box Set next year in October. But here is the catch. they have sort of recast the Third Doctor with Tim Treloar who will be the narrator and provide the voice of The Doctor. The Third Doctor box set will be in the same vain as The Companion Chronicles and The Early Adventures with the exception that one of the companions will not do the voice of The Doctor. The set also stars Katy Manning and Richard Franklin and will contain two stories Prisoners of the Lake a UNIT story by Justin Richards and The Havoc of Empires a space tale by Andy Lane. Here is what Big Finish said about the casting.
“As with our Early Adventures, these stories will authentically recreate the world of the Third Doctor, while paying tribute to the brilliant incarnation created by Jon Pertwee. We don’t see this as recasting the Doctor - Tim is playing the narrator, who in turn performs the Doctor’s dialogue - but the effect is so convincing that Katy was constantly praising his work during the recording.”