What percentage of bitcoin investors are gamblers ? Where will this figure be if we consider worldwide users ? I think it will be somewhere between 10-20% ? Also, it is possible that most of gamblers are still not bitcoin investors ? I see less chances of the later happening.
I think you are asking all questions and the percentage of your guess may not be confirmed. But I think the exact figure can only be known if a survey is done on that across then we can be certain what it is.
On my personal response, I won't talk on percentage but what I think is quite a handful of bitcoin investors will be gamblers and reason is they all involve same kind of exposure and purpose. Exposure in the sense that it follows almost same process of internet education and information. Moreover, they both relate in ads interchangeably, meaning you can see gambling apps on an exchange or bank online app.
Therefore, the ultimate goal is for profit. So it is not unlikely to find an investor in bitcoin trying to also leverage on gambling and the same goes for a gambler trying to leverage on bitcoin investment especially with the bull on the corner.