Anyone who claims that transaction volume moving to another blockchain won't destroy the value of Bitcoin is either delusional or lying.

Bitcoin's status as digital gold is backed by the demand for it as a transactional currency. All of the speculative demand for Bitcoin right now is based on the potential it has to carry on it a substantial portion of global finance. Bitcoin won't survive as an expensive to use competitor to SWIFT. It needs to be extremely cheap, and have space for millions of people.