Those things takes time. It has taken five years for Bitcoin to be where it is now.
Even if something so insanely smart so it is to Bitcoin what Bitcoin was to whatever was before it (e-Gold?), you probably have five years of trading between Bitcoin and the new hotness before it could possibly be "dead" in any way.
And some people are going to be early adopters, trade in their Bitcoins the first few years (and any new cryptocurrency WILL be denominated in Bitcoin the first few years, that is completely and utterly irreversible) and make a fortune. And there will be discussions again how be new currency favors early adopters and is unfair. History will repeat itself in every way.
But before that there's going to be thousands upon thousands of scamcoins which do not improve state of the art in any way and will ultimately be worthless. If you do not realise the new hotness before anyone else and move with the average pack, you will still be able to trade your Bitcoins pretty much 1:1. Roughly.
This is the one future prediction I can and will make of which I believe to be absolutely certain.