...who's to say they won't add some other typings as well?

What additions would you like to see the most? For me:

Grass/Dragon Sceptile - the other Hoenn starters have two typings - so should Sceptile.
Fire/Water Torkoal - that one has been mentioned a lot here, and it fits perfectly.
Bug/Ground Pinsir - Heracross has a second typing, so should Pinsir, and Ground would work great with Mold Breaker.