Profit possibility for colluding with 51% attacker
The Bitcoin Wiki states "A profit-seeking person will always gain more by just following the rules, and even someone trying to destroy the system will probably find other attacks more attractive."


The statement from the wiki has since been proven false. If a pool has a large enough percentage of the mining power, then it can follow 'selfish mining' procedures to earn more than it's fair share of the block rewards. This was introduced in this paper: http://arxiv.org/abs/1311.0243.

That is one reason your doubt in the wiki's claim is justified. The reason you cite, the two nations taking a bet on the price of a BTC, may be another possible case, but it doesn't seem very realistic to me. I'm not sure why any nation would take part in such a bet, and I think there would probably be more cost effective ways to lower the price of a BTC rather than engaging in a 51% attack.