Is it possible to enter undecided and then transfer into Architecture or Industrial Design after a semester or a year?
Yes. A portfolio review is required, so if you are already planning to attend JMU in the fall, I believe the earliest portfolio review date will be sometime in the fall semester.
If you are a HS senior, you may want to consider going through the portfolio review process prior to admission.
I am sure if you contact the School of Art Design and Art History they would be happy to answer questions for you. 