All this might have to happen in a frantic week!
Well I don't know about that. More likely we will see fees trending upwards over several months until an equilibrium is reached.
I think it is terribly sanguine to just assume that alternate chains can appear quickly and integrate seamlessly alongside the main blockchain.
I agree, but alt chains are already in development. When I say that they will appear, I mean that previously unused or rarely used networks may gain popularity.
Is coinbase an "alt-chain" in your example?
Hmm...no, coinbase is not an alt chain. They are merely an exchange. Ripple is an example of an alt chain.