Not impossible, but I hope not because that would still make Chespin's line super weak against Fennekin's. The grass/steel will be 4x weak to fire, so it would have a disadvantage over the other 2 starters.
Wouldn't Fire/Fairy be a better typing competitively than Fire/Psychic? Quad resistance to Fairy, takes neutral from Steel, and can obliterate Dragons. That's probably the top three of next gen at this rate, so all the better for Fenniken.