You would have to make a judgment call on when to move on. In cases where there's NPC exposition, you can post without waiting for everyone to participate. Otherwise, if there's a situation where you think a player might want to do something, you can ask, "What do you wish to do?" If you have the sense that a specific character might (or should) do something, you can call them out based on the situation: "So-and-so, are you going to do anything about the bugbear that insulted you?"
During combat, I'll give people a couple of days if it's their turn, as I understand that RL sometimes gets in the way. If I feel that their absence is going on a bit too long and they haven't given me any news about why, I'll play their character for them.
I think sticking to your post schedule is a good guideline, especially since you've asked for just 2 per week. You decide whether to spur the posting on to increase activity, depending on the circumstances.