I'm sure that bitcoins will be superseded by something with characteristics similar to btc, but easier to switch to traditional currencies. Bitcoins are a really smooth way to transact online, and the banks are probably trying to copy some of its features.
The methods of exchange for traditional currencies aren't a property of bitcoin; they are property of the traditional currency financial networks.
Please enlighten us, how this alternative currency you imagine is going be made easier to switch?
Should you have an answer, whatever your answer is, what stops bitcoin adopting it too?
It bitcoin is superseded, it won't be because of exchange mechanisms. Most likely it will be superseded by Bitcoin2 when the developers want to make some huge revolutionary change, and it will probably be capable of importing all the transactions from bitcoin1. The network effect is what keeps bitcoin at the top of the cryptocurrency tree.