Russia and China will probably do well without democracy for a long time, maybe centuries. They may spend centuries supporting their idea of mixed tyranny and industrial markets.
But they are in fact never going to be robust economies because they are parasites, in the biological meaning of that term. When democracy and industrial markets are combined you get innovation and new markets. Russia has always, in its former incarnation as the USSR, been forced to buy Western factories, use Western market pricing and copy Western innovations in technology. They can only survive by borrowing. The same is true for China.
That will not change. The combination of tyranny and industrial markets will always trend toward the status quo. The world will stop growing without the democratic free market nations....they (we) are the locomotives of the economic train.
The tyrannies will need us. Just as the socialist economies have needed us for the past fifty years.