You don't automatically download anything added to a collection after you've subscribed to all the items in it but you can favorite them and check to see if anything has been added after you've subscribed to all the items in it.

Basically, no but people can always check to collection to see if anything new has been added and the subscribe to anything that's been added.

Thanks I have a couple more maps coming before I make a collection. I am hearing that if you download a collection, you don't automatically acquire new maps added to the collection after you first subscribe. Not sure if true?

You may want to make a collection of all these maps.