I could see types going like this, starting from what I think is most likely and descending from there:
Grass/Flying, Grass/Dark or Grass/Psychic
Fire/Dark, Fire/Steel, Fire,Fire/Electric,
Water/Fighting, Water, Water/Steel
I know suggestions of a burrowing owl have been made, but even if it is a flightless bird with a secondary typing like dark, I think it will still have a lot of access to flying type moves like Roost, Air Slash, etc.
I really do think the water starter is gonna be part fighting (and I wouldn't mind). They seem to favour that as a type pairing combination for starters, but are gladly not always assigning it to the fire starter. I know Ice as a secondary typing is being suggested, but I personally sou t they will do this because ice is weak defensively and if it is a seal/Sea lion inspiration, then adding the ice type would make it too similar to dewgong and the like.
As for the fire type, I know people are saying that electric is too much of a stretch, but I do think its possible (even if its less likely) we had never had a psychic or dark secondary type for a starter before X/Y, so there is a first time for everything. Steel I could see for the claws, but Dark seems the most likely (although I'm not sure what kind of selection tigers have in mythology. They might be seen as more "pure" or "good" beings and the dark typing won't fit. Just plain fire might happen too).
As far as design, I'm hoping for more feral and animal designs as opposed to Bipedal/anthropromorphic designs. I'm not against he latter, it's just that we JUST had that with X/Y and ORAS and feel it will be more refreshing. I like the X/Y starter designs a lot, but prefer more "monster" like Pokémon typically.