What if Emperor Matthias and Anna of Tyrol have a son (Maximilian, b. 1612)? Max would be just 7 at the time of father's death. Would Matthias secure election of his son at least in Bohemia and Hungary? What about Imperial election? While Bohemia and Hungary had kids elected as kings before (like Matthias' great-uncle Louis II) it wasn't custom in HRE. OTOH if Max is elected as King of Bohemia then he'd be elector himself. What is going to happen in 1619 in such circumstances?