What you say may be true. But bitcoin's value proposition lies in those few lines of code. And that is why they will never be changed.
Bitcoin was meant to be an e-payment method (decentralized, trutless, etc.). A fixed bitcoin supply is not necessary for that goal. Indeed, bitcoin is being used in that role, in spite of still having 10%/year inflation (and even higher in the past). And dollars and euros work fine as payment methods, in spite of their "horrendous" 1-2%/year inflation rate.
Thus, the argument that "raising the emission limit would destroy the value of bitcoin" does not sound convincing. Hoarders would be very unhappy, of course. Miners, however, may someday find it advantageous, especially by the time they are expected do depend on transaction fees instead of block rewards. Block reward is steady and predictable, whereas fees depend on transaction volume -- which will probably shrink substantially if fees became mandatory. People who use bitcoin for payments may not care, or may prefer block rewards because they provides "free" transactions.
It has been argued that, if some miners tried to change the protocol, the rest of the network would stick to the old one. However, this correction mechanism has never been tested, and it seems difficult to predict what would happen, in all possible scenarios. (After all, it was "proved", with the same certainty, that altcoins would die as soon as they were born.) What if those "some miners" had 70% of the hash rate? What if a large subset of the users became convinced that the change was necessary for the health of the network, or got some immediate benefit from it (such as no-fee transactions)? What if payment processors and merchants accepted only the "new" bitcoin?
(By the way, some bitcoiners seem to be trying to convince people to adopt bitcoin by telling them that money sucks. I sense a problem with that marketing strategy: it seems that many people have used money sometime in their lives, and may even have enjoyed the experience -- unlikely as that may sound.

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I have to side with Jorge here. It is unlikely that coin emission will change in recent times but it is not impossible.
Ultimately you cannot enforce what rules people subscribe to. The mere existence of altcoins proves that multiple rule sets can concurrently exist.
And no one should fool themselves that only one coin will ever be accepted by retailers. If it is trivial to integrate bitcoin, it is trivial to integrate other coins.
The proposition that only bitcoin can and will survive comes from selfish motives. You only need to believe in that if you want its value to be extremely high.
There is enough room for multiple cryptocurrencies and they can and will come and go as technology changes.
Does it really matter if I pay something in btc, ltc, doge, nxt or ether? If the design and security of the protocol is sound (which I am not advocating here for many of the so called bitcoin 2.0 alts, the verdict is still open) and enough people use and accept it it is "good enough".
Arguments on the network effect only work to a certain degree. An analogy would be to claim that something like Facebook or Google will be the sole existing service simply because it has the biggest network.