In order for the above scenario to completely work out, you have to assume that the Patriots do not end up with a cornerback of Talib's caliber on the team. While many fans will be ready to jump ship if the Patriots don't get that guy during the free agency period, you really need to wait and see how next season pans out. The Patriots do have some guys (Logan Ryan and Alfonzo Dennard) who have shown an awful lot of potential. Maybe they will take it to the next level.
When other people look back at the Patriots' defense after Talib went down in the AFC Championship they seem to focus on what we couldn't do without him. While I think things did fall apart without him on the field, I think part of the problem was the coaching. After the game Belichick kept saying that he could have done a better job. I think he looks back on the game and realizes that the defensive game plan had to change with Talib on the sidelines. Usually the master of adjustments, Belichick didn't make changes to the game plan and it didn't work out.
Now in order for this gamble to really pay off for the Broncos, Talib will need to remain healthy throughout the post season. While that might happen, I think it is pretty unlikely.
Regardless of what happens in the future, I think Talib was overpaid. However, if the Broncos end up hoisting the Lombardi Trophy, then it is worth it for them.