The reason for this is primarily because FCA needs more office space, and the company decided to convert the museum for that purpose. The the cars will be moved to storage after the closure, and they'll be shown at various events. However, they'll only be able to be seen together for two more weekends. Those weekends include those of November 19 and 20, and December 17 and 18. The museum will be open from 10 am to 4 pm on those days.
If you can, we highly recommend visiting the museum. Adults get in for $10, seniors and retired FCA employees for $8, kids between 6 and 17 for $6, and kids under 5 for free. It also has some fantastic cars including concepts from the 1950s to the 2000s, oddball performance vehicles such as the Omni GLH-S, and of course plenty of fascinating history. And if it makes any difference to you, there's even a purple Plymouth Prowler you can sit in. Just make sure you don't wait too long to make up your mind about visiting.