So does this means that due to today's 1 MB limit per 10 min (i.e. per block), if the number of transactions get so large that more than 1 MB of transaction data is generated every 10 min, then some transactions will never ever make it into the blockchain, if their transaction fees are too low?
Then this means that the queue of transactions that are waiting to get into the blockchain will grow larger and larger all the time, because the rate at which new transactions are created (> 1 MB/10 min) would be higher than the rate at which transactions could be processed (== at maximum 1 MB/10min).

If this is correct, then there would be the following consequences for the future of the bitcoin system, as transaction volume increases:
(1) Only transactions with sufficiently high transaction fees will make it into the blockchain at all.
(2) The Bitcoin clients should get a feature to revert transactions that are not yet in the blockchain, because if I transfer 1 BTC to address xxx with a low fee yyy, and after some days or weeks my transaction still does not show up in the blockchain, then I might want to revert my transaction and try again with a higher fee zzz > yyy.
(3) As a result of this mechanism, there will be a real "fight" to get one's transaction into the blockchain, so in practice this means that transactions will no longer cost "almost nothing", but to the contrary, transaction fees would soon become so high that for example micro-payments and small donations become prohibitive due to the high fees, and it would soon be cheaper again to use PayPal!
(4) As a result of (3), people will move to make bitcoin payments more and more inside "closed sub-systems", i.e. bitcoin banks that do their own bookkeeping on their customers' accounts without loading the blockchain. For example there could be a MtGox subsystem or a blockchain.info subsystem, to name just two. When I transfer BTCs from my MtGox account to another person's MtGox account, I would not use the blockchain, but the MtGox internal bookkeeping would carry out the transaction, just like in today's banking system. This would avoid transaction fees, so people will favor this variant. But this also means that many benefits of bitcoin as we know it today would vanish, and the whole bitcoin system would move towards a de-facto centralized system that is again built on trust into a cartel of a few "subsystems" (bitcoin banks), and these sub-systems may even run fractional reserve banking without their customers knowing about this.
So we would again end up with two kinds of money like in today's fiat money system: First the true bitcoin money (corresponding to today's fiat central bank money), and secondly the account balances of the "subsystems (=bitcoin banks)", that may finally run fractional reserve, like today's bank accounts.


Also, these sub-systems (bitcoin banks) would be vulnerable to government interference etc. So with such an evolution we will reach the point when the bitcoin experiment has finally missed its original goals and has failed. I think such an evolution should be avoided!

If my understanding is essentially correct, then I think the only solution to keep the bitcoin system open and avoid the outlined evolution towards closed sub-systems (="de-facto-bitcoin-banks") would really be to change the way that transactions are stored, as outlined in my last post, such that memory needs for saving the blockchain (be it the complete history or only the current state plus a short incremental history) does not increase infinitely.

Maybe my thoughts are relating to what may happen rather far in the future, but this future might also turn out to be nearer than what we think.

...Or am I missing some fundamental point here and all my worries are pointless?