Yes, no great power or superpower (US) will risk WW3 over Crimea. 2050 and out, the answer becomes a maybe. Russia will really be a shell of itself by 2050 and esp. 2100 with a dwindling population. Would the need to retrench present itself due to fiscal/internal political restraints. Possible but understand that Crimea has a lot to do with Russia's ability to project power, esp re its lack of ports.
Which would open the door for China (by which point, it will likely surpass the United States in having the largest economy in the world) to engage in similar behavior, like reclaiming Mongolia and other territories once occupied by the Qing Dynasty empire at its height:
Only a strong Russia under Putin is preventing them from doing so. Once that changes....