Bachmann realistically are only going to produce items if they think they're going to sell. Numerical order won't guarantee sales - popularity of the characters will. Sir Handel has barely appeared in the show in recent years, whereas the likes of Peter Sam, Duncan and Rusty have been far more frequent.

If I were a betting man I would place money on Rheneas being the next narrow gauge engine introduced, followed by Rusty and then Peter Sam. I can't see Sir Handel being produced for some time.