A scam is probably not a suitable term for Bitcoin - there is no dishonest scheme with malicious intent from those who are behind the technology.
I don't think Bitcoin will collapse, but rather will lose its popularity. Now, Bitcoin is more of an asset than a currency, like a collectible. It is worth what other people are willing to pay for it. Like Beanie babies or fine art.
It has fundamental issues that make it difficult to be adapted as currency (those "issues" are seen as "advantages" by many). If Bitcoin proves difficult to be adopted by a large portion of population, it will start dwindling down until forgotten by most.
It will still be used for transactions that people want to keep hidden from the authorities. I'd speculate this will happen in 10-15 years.
Scam could only be tagged up into those activities that surrounds on bitcoin market on where it is been mainly used for those criminals on making use of its anonymity feature which it is really sad
but cant really be avoided this kind of reality on where people would really be taking some advantage on regarding with this but talking about bitcoin on being directly as a scam isnt really that
appropriate or doesnt really fit out because demand is there and you could see on how big the community is that do support this coin.