So now that the preseason is done has he?
Absolutely! In fact, I'd go as far as to say that if Alfred Morris gets off to a slow start he'll lose carries to Seastrunk.
Morris already will because he's not a threat in the passing game at al. In two seasons with the Redskins he has only caught 20 balls for 155 yards. So even when they did throw it to him he didn't do much with it.
Seastrunk does not have a history of success in the passing game, but he certainly showed against Tampa Bay he can be a threat in the screen game and just catching the ball in the flats (see above).
He's not the biggest guy (5'9" and 200 pounds) so he may not have much success running inside the tackles, but with the way the game has evolved the team will probably not ask him to. He is going to be at his best at least early on in his career in space (i.e. sweeps, toss, and anything else that goes outside).
Can he be the next great Redskins running back? Right now he doesn't look like someone that is going to get the ball enough to earn that moniker. He'll need to add some size while not losing his speed so he can become a more multi-purpose back. At the time he appears to be more of a Pierre Thomas or Darren Sproles type player.
There is nothing wrong with that of course. Those guys are exciting as hell to watch, but should he continue to perform as he did in the preseason the sky is going to be the limit for Seastrunk.