M.S.
whatever you do, do NOT let him watch movies, etc. because if he figures out you will let him, even if only occassionally, he might just decide to make it a nightly habit. it is early, so you still have time to fix this problem...
you need to take him back to bed, every time he comes in... this may happen a dozen times, depending on how stubborn he is, but you have to out-last him. he will eventually figure out that nothing will be gained by getting out of bed. also, pick a parent... if you take him back tonight, your husband can take him back tomorow... just don't change it up on any given night because then it becomes more of a game. don't turn on any lights, don't respond to any requests for juice, water, etc. just walk him back to bed and tell him is a calm voice it is time for sleeping, and that he needs to sleep in his own bed.
you might also try putting a gate in the hallway for a while, my daughter had a phase of this, but now she might open the door, see that she can't go anywhere and then goes back to bed because it is dark and boring.
it is harder in the short run to do this, and you may lose some sleep over the next few nights, but keep your eye on the long term goal here... good sleep for everyone. remember, while you are tired and losing sleep you also want to remember that this night waking and getting up and watching tv. is not a habit you want your son developing either.