Actually that text doesn't specificly mention that the cubes is for the variant. They say all the tokens is for "future use".
Too all of our valued customers,
Due to uncertain wood supplies, your copy of "Steam" may contain additional wooden player markers with colors that vary from those described in the rules. You may also find black load cubes. These pieces are for use with future variants, which may include extra players and special rules. Set them aside for future use. Please enjoy your game knowing that these color variations will not affect game play.
To me this sounds as another way of saying that they made a mistake, and that they will try to come up with some rules that uses all of these pieces.
- which again means that we not likely to see the wooden train pieces we have been 'promised'. What would the point of deliberately deliver several set of player cubes in wrong colors and then later have people buying locomotive tokens in the same new colors. And even *I* would never attempt to play a 10-player game.