Short of a major strategic change (like de-hubbing Cleveland), it is not going to happen.

Reasons:
- Not enough aircraft to support a new hub without de-hubbing CLE and/or significantly down-sizing EWR or IAH, which do not seem likely.
- Too much competition (mainly UA and Frontier)
- DEN is a good hub for domestic traffic in the west, but doesn't fit their strategy of focusing on international travel. DEN is not far enough west to serve as an Asian gateway, for example.
- Not enough O/D traffic. While better than CLE, CO has definitely found CLE to underperform EWR and IAH, due in large part to the lack of O/D. US had the same issue at PIT. DEN would be better than CLE if it weren't for the competition with the existing incumbants. There just isnt enough pie to profitably split another way.

I think if they had not made the decision to scale back the Barbie-jets, they might be able to make DEN a western ERJ mini-hub. But since they cut those back, there aren't enough aircraft to make it work.

Once the 787 comes, there could be a desire for a western hub as an Asia/Australia gateway. But it would most likely be SEA, or possibly an LA or SF-bay area airport.