Anyone who thinks Russia and China would (a) ally together (China has irredentist claims on Siberia that are far more likely to start a war than not) and (b) would form some form of "great power" if they did magically set aside their differences needs to redefine "great power." By the new definition you're proposing, Chad and Nigeria would be a greater power than China and Russia.
China is Enron with nuclear weapons. Russia is a bankrupt nation with nuclear weapons. Pretty soon, China will hit the same great crash...and the question will be "will the first nuclear civil war be fought in Russia, or in China?"
If you're looking for an Axis...my bet would be on a German-South American Axis as the most likely one.
Red China and Russia unite to create New World Order says communist newspaper (6/18/01)
Russia, China sign historic friendship treaty (7/16/01)
Jiang calls for new order to counter US (7/17/01)
Russia to hold military drills with China:1st time in more than 30 years (4/28/02)
...and (b) would form some form of "great power" if they did magically set aside their differences needs to redefine "great power."