Question:
If I upgrade, does the 20,000 point bonus reset the clock on the 24-month bonus rule, thus thwarting my plan to reapply for the card in late 2019?
AFAIK, Chase never offered upgrades with a bonus on any card before, and so there's no history of this. If so, we'll have to wait until some tries this and reports back to figure that out. So for now I would assume it does reset the 24-month bonus rule clock until/unless it's proven otherwise.