Yeah but in general people relate how much they want to gamble in relation to fiat. If BTC was half our value, people would take bets twice as large. And vice versa.
Exactly this. In the long run we may play with less BTC but if FIAT value of our bets stayed the same, so I guess nothing is changed.
And I don't think it is that important for casinos, if they wish the might convert BTC to FIAT if they expect a market collapse anyway.