There is an acknowledgment in the game that the Guardians of the Galaxy are a team. However, the game will insist that the player only plays as Star-Lord, since he is the Guardians of the Galaxy’s leader. So, no switching from Star-Lord.
As the game was being developed, there was some thought of letting players cycle through characters. Eidos Montreal, the developers of the game, chose not to let the player switch characters.
This news was revealed shortly after the game was announced. Guardians of the Galaxy’s Senior Creative Director, Jean-François Dugas, said in an interview with IGN:
Because of this, the game is more focused on tactics than on straight action. The developers wanted players to think about the actions of the Guardians and the consequences of each situation. It’s a very strategic game.
For more info on Marvel’s Guardians of the Galaxy Game, check out Is Guardians of the Galaxy Multiplayer or Co op? on Pro Game Guides!