I'm not myself claiming that alternative chains would be successful; I'm referring to some earlier posters' assertion on this thread that the demand for higher transaction rates would be met by new parallel blockchains popping up (once block space on the main chain becomes too scarce).  My claim is that, IF new chains were starting to become very widely used (as they would have to be to maintain a high transaction rate), there is no particular reason why coins on the main chain would continue to remain much more valuable than coins on the new chains in that scenario.  And if the overall supply of coins (on all widely-used chains) goes up, that is overall money-supply inflation, which would tend to depress the value of existing coins further.  IMHO, it would be very undesirable for the value of BTC to allow a lot of competing cryptocurrencies to pop up and be successful.  A good way to let that undesirable outcome happen would be to fail to upgrade Bitcoin to support some critical property that is (or soon will be) in high demand, such as scalability to high transaction rates.