What is the deal with all these Broadway shows?!?

i just was checking on the internet to get show tickets for my mom and me to go see a couple of shows. i checked gypsy, Greese, all my sons, young Frankenstein, and a couple other shows as well. i am going in less than a month, and i am looking for tickets, and either all the shows are ending around the 4th of january or cancelled! whats up with this?! if this keeps continuing, are we going to have any Broadway shows left to see? the only one i want to see that is still open is in the heights. why are all these shows closing or being cancelled!?! that dosent even include spamalot, hairspray equus, spring awaking, 13 and a whole junk load more!!!! does any body know whats up?