I think bitcoin is getting more powerful everyday as more people are learning about it and therefore using it or even mining. I can only find 3 reasons for which the bitcoin will not be thriving in 5 years.
1) The government makes it illegal claiming its a threat of security because its anonymous and its being used in illegal markets. (war on drugs etc)
Not that this would stop bitcoin completely as it would still being used for illegal reasons.
2) Internet crashes.
I read somewhere that it could be regulated. Which means put taxes on it. This would also be a wound but not that severe to stop something that will be too powerful by the time its regulated.
The 3rd scenario is that bitcoin is SkyNET and it will take control of all the machines(and Arnold).
In that case all we can do is stop mining, sell all the bitcoins and pray for John Conor^^
