That's arguing that the past will be like the future when things are still really early. Statistically almost nobody owns or uses Bitcoin, especially when you subtract the Bitcoin proponents who do most of their transactions using something like a credit card which actually uses local currency via Visa or where Bitcoin is converted into real currency immediately by the recipient, and who thus would have very little switching converting to something else.

Ask how long either #1 or 2 would hold true if, say, a couple of large banks, Visa/Mastercard, Apple and/or Google, etc. launched a currency accessible to their existing customer bases. I'd give that a couple of days before Bitcoin would be a rounding error in the daily transaction volume.

The big long-term reason I expect that to happen is the deflation model baked into Bitcoin: every player which didn't acquire a substantial holding years ago has a huge incentive to find an alternative which doesn't mean they're putting effort into making someone else rich. Right now there's very little mainstream demand for Bitcoin but if that change it's hard to believe the finance people wouldn't be obsessed with ways to capture that revenue going to a third-party.