Those fall more on the commodity side of the spectrum in my opinion, along with being CONSUMABLE GOODS. People want different flavors because there's no difficulty when switching between them, but do people want to use multiple alt/crypto currencies? I doubt it, it's an inconvenience and we all know how humans dislike changes and things that bring inconvenience. Just like there is one fiat currency for most nations, there will be one dominate crypto currency IMO. Now that's not to say that a few alternative currencies may find a niche in a specific market somewhere, but they just won't be used by the masses.
What I'm saying is
markets prefer choice. Some people are die hard Pepsi drinkers, others Coke. As long as there are enough people that prefer a certain brand, for whatever reason, that brand has value.
I don't know if you've visited BTC-e which has the famous chat box, but there are some pretty die hard Litecoin fans, ones that are just as set about Litecoin as others are about Bitcoin. The fact that there can be irreconcilable opinions is what led me to realize alt-coins had a crucial role to play. This dawned on me because I was involved in the opposition and uproar over the announcement of a power consolidating Bitcoin Foudation, a topic that to this day is a problem issue to some.
What I realized was that as things progressed there would be individuals with differing views on large enough issues as to be problematic. Keeping everyone happily under one tent seemed implausible.
Yes there will be many people that only hold one main cryptocurrency or another, but there will also be those that hold multiple ones. Technology allows for instant and easy exchange and transfer of any cryptocurrency, so the inconvenience of having more than one is practically non-existent. Remember, conversions can happen within seconds and behind the scenes.