Honestly, it's very difficult to say what Russia will do after 10 years or so. China could be a $30T economy, Russia could be a piddly $2.5T economy. Then one can imagine what it will be like 20 years from now, when the difference is going to be even more stark.
Russia has dropped its target of becoming one of the world’s five largest economies in a sweeping reset of its ambitious national development goals.
www.themoscowtimes.com
Russia could either end up falling under China's influence or ironically end up joining NATO to counter the Chinese threat. I don't believe Russia will be able to find a middle ground to co-exist with China beyond a certain point.
As for the weapons, I don't think there's anything there. The Chinese ripped off Russian weapons to build up their own industry. But the majority of their export products are now their own designs. Any passing external resemblance are not covered under global IP laws and are barely anything significant enough for Russia to contend with. For example, the Buk/Shtil transformation to HQ-16 now incorporates mostly Chinese tech. But at the same time, they are unlikely to cross the line by exporting their Flanker rip-offs. The new Chinese products have basically started competing with the Russians in traditionally Russian markets though, and that's bad enough, but it's just a new competitor. India will also start stepping on Russian and Chinese toes at the export market in a few years. The only way out for Russia is to diversify into the civilian domain and make stuff that regular global consumers want. One little advance in battery technology can kill the oil industry after all.