What would be the value of Bitcoin if coin generation was complete and Bitcoin was strongly accepted today?
If it so happens that bitcoins are as widely accepted as USD are today, then yes that's a roughly reasonable estimate. 

You might enjoy the following link for some more thoughts along these lines:
http://falkvinge.net/2013/03/06/the-target-value-for-bitcoin-is-not-some-50-or-100-it-is-100000-to-1000000/

(One side note: just because new bitcoins are slated to stop being created in 2140, that doesn't mean no more new blocks will be created. Blocks are essential to record transactions, and they'll continue being appended to the blockchain even after the bounty drops to 0.)