Go to the developer forum and you'll see some guy is offering Bitcoins to developers to help him start up his own blockchain and corresponding client, and miners to help him mine the new currency (he calls it Groupcoin).  So anyone can do it, but just because you can doesn't mean they'll be worth anything.  Bitcoin is worth something because it has a large number of people on board.  People have a hard time understanding this.  I think the Groupcoin founder believes he's going to get rich and spread wealth to all the developers who help him (and some are).  But before you invest your hard-earned Bitcoins in Groupcoins, remember that Bitcoin is worth something because of the number of people who use it, not because of some secure P2P accounting system, brilliant though it may be.

This is exactly what will occur to bitcoins, Once the limit is reach the amount of users will drop, The places of which accept bitcoins will also decrease, And the value will drop.