i expect an abrupt end at some point.
some countries will fight BTC with legal threats to the users and miners but at some point they will realize that they can stop BTC with as little as some million $ to crack the 50% network barrier. If this happens over night, there is no way to recover. The block chain will be finished. This rogue subnet will be kept at 50% and BTC is history. Maintenance will quickly go down as running a miner with 0 output will not pay off for most of the other users. This person behind such an attack would not even have to justify his action and could well be some rich guy protecting his hard earned dollars from becoming obsolete.