One of the interview said that the powers are related to resources that were abundant in the game. We've already seen the bad guys using Earth/Concrete, so I would assume you could get that power. Water is everywhere in the game, there are puddles of water on every street and Seattle is well known for it's rain - I would be surprised if there wasn't a water/rain power. Metal is also featured predominately in Seattle and gameplay videos (cars, buildings, structures, sculptures), I could imaging this being a power, possibly an epic moment where Delsin brings down the Space Needle? Wood? There are trees all over in the game along with pallets, wood benches, tables, chairs on every street.
Aside from that I personally think Cole (more along the lines of a Kessler) is in the game and during a special mission will grant Delsin all of his powers, Delsin unleashes every power we've seen Cole use and then some. At the end of the mission Cole takes his powers back (after revealing he has the power to take away powers).