But would there be no effect on Bitcoin's re-growing dominance if there was enough altcoin "straight to fiat" liquidity? Because most of the altcoins do not have fiat markets, only Bitcoin markets.
I guess the "dominance-boosting" effect would be even stronger - altcoiners (or better: "shitcoiners", as not all altcoins are shit) would directly cash out to fiat and the altcoin price would go even faster near zero, without touching Bitcoin (Bitcoin also can be driven down by altcoin sellers cashing out via Bitcoin).
How many more banks use Ripple?
Don't know. On their website they list four "testimonials", some of bigger banks like Santander (the German bank I mentioned isn't among them).
But do those banks that left their "testimonials" on the site use XRP everyday in their banking organization? I believe there's not one bank that uses XRP or see that they need to.