I just don't see someone buying that entire collection just because they have the money and want bragging rights. I could see that scenario on a single poster (or maybe a small handful) that are very, very, very valuable. But having a ton of posters that range from common to rare just doesn't seem (to me) that interesting of a purchase for someone to blow their disposable money on. Sure there are a few very rare posters in that collection, but they could be obtained individually for far less.
People with that type of money, who want to show off their stuff, want individual items that are easily displayed to impress their friends and colleagues. No one is going to fill an entire room in their mansion with random Star Wars posters for that purpose. Trying to display such a collection would really be inconvenient. For that amount of money, that could buy something much more impressive in the Star Wars collectible arena (like an original screen used Yoda puppet, or something else that was actually in or part of the movie itself).
Just like rich people who collect cars. Someone might not blink an eye dropping $1,000,000 on some super rare antique car, but I don't see them spending that amount just to have one of every single model that Ford ever made.
I think the only hope of that lot ever selling as a complete unit is for some die-hard Star Wars poster collector to win the lottery and be just completely reckless with the proceeds.