While the OP seems to be putting his finger on a growing TREND of alt-coin growth, I can't see how multiple coins with or without technical innovations over BTC can fulfill the dream of being an effective extensions of BTC.  The end user is simply never going to juggle ownership of multiple types of coins, just as people who are not currency-exchange-speculators do not simultaneously carry dollar/euros/yen in their pockets to buy things with. 

Money is a 'natural-monopoly' because its a network-effect ware the utility is proportional to the number of people in the network.  All crypto-currencies have appallingly small networks and low utility compared to national currency and the alts are even lower, so nearly all value is speculative in both.  Speculators can and will deal in multiple currencies, real commerce will not so an inevitable 'winner take all' will happen and everyone knows this.  Speculators are speculating on which coin that will be, not on actually proportional value in a mixed coin environment.  The current mixed coin environment must be transitory, and to what ever degree we have continual mushrooming up of alts they will always be alts in the shadow of the king-of-the-hill.  This is not to say the king can't fall, but if it ever dose it will be replaced by a new king.  In other words Cyrpto-currency will always be uni-polar and never multi-polar.

Another factor to consider, when most of BTC's perceived value is from encoded scarcity, the existence of a multi-polar world of alt chains that trade at comparable values and constitute any significant portion of commerce.  And particularly if they show potential to expand without limit, would completely negate the scarcity concept in BTC, as while the BitCoins themselves would be scarce their would be virtually unlimited numbers of adequate substitutes in the marketplace.  And any Econ 101 student will tell you, adequate substitutes trade as a pool.