Most Fire-type starters tend to be based on an animal in the Chinese Zodiac (Fennekin somehow broke the trend but some consider it to be the Dog since foxes are canines) so maybe for the next one I'd like to see a rabbit, because I recall seeing a Fakemon design of such a thing and it looked pretty good.
Grass-type starters have mostly been reptilian, although Chespin became the first one to not be reptilian. Still I have a feeling we'll get another reptile or something.
And Water-types are mainly amphibious creatures, as has been seen with the ones so far, so maybe they might stick with that route.
(sorry dude my internet connection has the hiccups)