There will always be a market for altcoins alongside Bitcoin because (a) they can remain completely anonymous and (b) pure cryptocurrency exchanges that do not

There will always be a market for altcoins alongside Bitcoin because (a) they can remain completely anonymous and (b) pure cryptocurrency exchanges that do not engage in trades for fiat currency provide an indirect avenue for trading in and out of official fiat currencies, via Bitcoin. With KYC and AML attaching themselves heavily to most Bitcoin exchange services, people will trade into or out of Bitcoin non-anonymously, and they'll trade their Bitcoins anonymously for another cryptocurrency. Those cryptocurrencies will then by used for illegal purposes and it'll be very difficult to prevent that value from being laundered back into legitimate currency because the exchange between different cryptocurrencies can't be effectively policed, especially once distributed exchanges get off the ground. In my mind, because of this, the whole field of KYC/AML restrictions being forced onto Bitcoin will ultimately fail or at least be extremely easy to circumvent, as long as altcoins exist.