Why would you think people are not going that high on betting online?
If I'm the one want to deposit huge money on online gambling site even though it is trusted site but still think that what if casino don't pay me back my winnings for a huge amount?
I believe there is not much different between online and offline, so if there is early adopter which is holding like 10k of btc, I do not think it is impossible for them to spend like 1k just to gamble here. For them, to have more coin means pretty high risk too to hold it for that long, so spend it on gambling will be the best way
Why do you think that anyone will scare or worry about holding a huge number of bitcoins for a long term? The best part of these cryptocurrencies is no one can trace who is the owner of those coins then why anyone need to worry?
Just because got more coins people will not waste money on gambling. if you want to spend your coins you can spend them to buy anything then why only gambling?