I agree with Dutchjet.
DIA will be fine. there are always rough waters somewhere, but the afflicted always make it through.
Besides, if UAL did fall, other airlines would be more than happy to fill the gaps at the necessary airports. Like UAL did at Stapleton when Continental left; I remember seeing an increase in UAL flights and size of aircraft. Delta filled the void at ATL when Eastern fell, and so on.
DIA is a great location for a hub, some airline will always have DIA as a hub.
"It's just some' a dat sticky spot in der y'all, mmmhhhmmmmm!!"
Ding! You are now free to keep supporting Frontier.