That seems to be the prevailing theory. Being migratory, the tribes would have moved to follow game and fish supplies....................
I had never heard that that theory before recently, and realized that I had been lied to in elementary school history class. We were told the colonists disappeared and only left that message on the tree, but the colonists did NOT disappear, they left and everyone pretty much knew over time that they most probably joined the Indians.
You have to imagine how much of the history we have been taught is lies or stretched truth. Especially now.