Ben Small who voices Thomas in the UK has promised more suprises in newer stories.
On his official YouTube Channel under the name of Benster71, Small confirmed the name of a new character in a later series;
He also confirmed that he will be voicing the new character along with a returnee;
However, Small did not confirm when both would appear in later episodes or series, although he did promise that the next special would deliver; Day of the Diesels is gonna be a good one!!!
Concerning that he didn't know much sites about Thomas, he went onto praise a well known team that are known across the internet...;
I only know about SIF, and have been blessed enough to have met the guy's who run it, whilst at the premiers of HOTR and MIR.
Day of the Diesels and the next series of Thomas & Friends premieres later this year.