Look at the funds, experience and resources the US had to play with developing the F-22A. It took them 15 years. If the Russians or Chinese want something comparable its likely to take at least that long (probably longer). I seriously, seriously doubt teh PAK-FA will be ready by 2015.
Actually, I think your number for the F-22 development time is off a little. The aircraft now known as the F-22A Raptor started out as the ATF (Advanced Tactical Fighter). The was first funded by Congress in 1985, given that F-22 reached IOC in 2006 IIRC then the programme was more like 20 years to develop the Raptor.
As for Russia being able to develop a 5th generation fighter... IMO yes, they can. Would it likely be as capable as a US fighter? IMO, no, at least not currently or in the near future.
I base that opinion off a number of factors listed in no particular order.
1. Economic resources: While money is the end all be all, the more resources available typically the more things which can be done.
2. Corporate knowledge/continous development: Even following the peace "dividend" following the end of the Cold War and fall of the Iron Curtain, the US able to continue development and testing programmes. In doing so, a measure of collective knowledge was able to be retained, Russia does not seem to have been in the same position for a period of time.
3. Flow-on development from non-military applications: The US has burgeoning civilian markets for electronics, composites, all manner of things in fact. This civilian market has spurred inovations leading to smaller, lighter eletronic devices, more powerful computers, lighter and stronger plastics, etc. All of these developments in turn contribute to the available knowledge bases used to design and manufacture military devices and components. Under the Soviet system, there was not an equally active civilian consumer market to either fund or spur such inovations. Also, given the economic issues Russia had after the Soviet Union broke up, as well as the ready availability via import of desired commodities, I would guesstimate that Russia is still in the process of developing civilian sector manufacturing.
A has been mentioned over and over again, it is not so platform specific, as a system vs. system response. The current and upcoming US 5th generation platforms have definate places with the US response system, and that having different, complimentary components working together the entire system is able to achieve effects.
Russia, which does not seem to have the same level of ability to operate together using disparate but complimentary components, would therefore not likely be able to achieve the same effect using a similar 5th gen platform. Given time (and sufficient resources) I expect Russia would be able to develop or build the supporting and interoperating capabilities as well as develop the required doctrine to employ them. But it would take time.
-Cheers