The idea of wallets with dozens of digital currencies ties in with another idea which I've been intrigued by recently.
Apart from the payment mechanism functionality, units of cryptocurrency are much like shares in a company.
The Cypherfunks experiment (www.thecypherfunks.com) illustrates this concept: Imagine anybody could own shares in the music industry. To make this possible bands simply accept payment in a specific cryptocurrency (e.g. FUNK). As more people support bands using this form of payment, the value of the cryptocurrency grows and the entire network of bands and their supporters benefits.