I honestly fail to see the problem. Why is it important that there be only -one- true coin?
Bitcoin blocks are getting full. so what? fees will drive up. It's survival of the fittest.
Scalability problem was solved with altcoins, 5 years ago when litecoin launched. Those who cannot afford the bitcoin fee, always have the option to move to an alternative, cheaper blockchain.

Look at the real world history. People used to trade gold as a currency hundreds of years ago. When It became to scarce and hard to find, it's value raised dramatically.
So poorer people started using cheaper metals i.e. silver, copper to do their daily business and gold became a high value currency that only those who could really afford it would use.
Nowadays we use paper cash because it's the cheapest method.

The same principle should apply to crypto currencies.. Bitcoin is the gold. litecoin is the silver, [insert random non scam coin] is the copper, etc.
Those who want to make small transactions, can use the cheaper coin, so (1) they can move money for less fees and (2) remove the unnecessary clutter from bitcoin blockchain.
And there is nothing to limit the scalability. once litecoin blocks get full, bring on the next coin, Dark coin maybe? when that's full, move on to the next
Increasing the blocksize limit DOES have a scalability issue. You force everyone to use a big blockchain. but by splitting the blockchain into multiple coins, the rich will use the bitcoin(gold), middle class would use the litecoin(silver) and the poor would use the feathercoin (shit). they don't spam each others' coins, and they use the blockchain they can afford.

You don't have to deal with hardforking issues either. it's a win win win for everybody.