Like the OP said, the microtransactions will probably move to LTC, DOGE, DASH,... since their blocks won't be full, so their fees will be much lower.
People here are very hyperbolic when it comes to the fees. It is not like they fees are going to increase tenfold over night just because blocks are full. It will take a while before more than half of the blocks mined are full. This is if we assume that nobody is doing anything in order to increase the capacity (which is obviously false).
This also does not mean, that it will be the end of Bitcoin. We saw what happened last year when some unknown group flooded the network with transactions and called it a stress test. Most people just paid a slightly higher fee and their transactions went through quicker.
If this situation happens naturally without someone trying to force it to prove a point, the developers will react and a proposal will be suggested to increase the block size. This will receive consensus from the nodes and the miners more quickly, because it will influence their operations directly.
There are no urgency now, because we hardly see full capacity without these fake stress tests.