I think Primecoin has a good chance if more merchants start taking it as payment.
A have been looking for a simple way to take Primecoins as payments. However as it is now there is no easy way for me to stick a plugin or Primecoin payment system on my web stores.
I have thought about paying for development of such a system.
At this time I am not willing to invest a few thousand dollars needed to implement it. Hopefully someone with more practical experience will come up with a solution.
This is an interesting point. All altcoins need this actually.
Someone should make a "bitpay" type service that allows payment in MANY altcoins, so that they become all accepted by merchants. This would really help the cryptocurrency economy as a whole.
Each different altcoin could be thought of as different types of coins.. in USD we have quarters, dimes, nickels, pennies. In crypto, we have bitcoin, litecoin, feathercoin, primecoin, etc. (although I'm aware that bitcoin can be nearly infinitely divided so this example isn't exactly the same, since bitcoin can be dollars, quarters, pennies, all at the same time)