The Islamic rules are often implemented and taught without truly understanding the point of the rule. Gambling is not allowed because of how it encourages taking advantage of people to take their money through the false possibility of wining money for nothing. Mining is not a comparable activity and hence cannot be considered haram on these grounds. If you intend to profit from selling your Bitcoins during the price hike then that could constitute as gambling (due to making profit from doing nothing) and hence could be haram.

Note, I am not a scholar nor am I a Muslim but from what I learned about Islam it appears that a thorough logical analysis is required when deciding the impact of new "things".