If people uninstall the client then it's done.
There's hardly a reason to uninstall it, bitterness is one.
For those who do uninstall it, they can still re-install it. Its not like bulldozing a bank, software is cool that way.
Bitcoin can't go away. Its impossible even if 75% of the user base uninstalled their clients.
I cashed out of mine-and-hold long ago because I recognized that bitcoin was overvalued and underutilized. But that's not a permanent thing. to me, bitcoin had little chance to grow when it was 5-20$ per coin. Now that it has settled down, i think its use is going to pick up due to new users who see the tremendous potential. Online poker is one way that could happen. I've personally made a bitcoin transaction in order to fund a merge network poker site just a few days ago. I believe Bitcoin will be back in a big way with online transactions. The price might stay flat for a long time, but price is not the point of bitcoin. Profiting in bitcoin is a bonus and has nothing to do with its usefulness.