It was known long ago that the Russians won't be mass producing the Stage 1 PAK FA.
There is no reason why one cannot produce Stage 2 PAK FA whilst skipping production of Stage 1.
The USAF has decided to modernise a whole lot of 4th gen aircraft whereas the RuAF is simply buying brand new, much more modern 4th gen aircraft. That's where Russia's money is going. And 5th gen tech will become available for the MKI and all other 4th gen Russian aircraft in the meantime. So it's not like the Russians will not be producing 5th gen avionics.
2016 was a long time ago? This project started in 2004 and the engines won't be ready for 2 decades.
And that's not the point. You know what the biggest advantage of getting to a new technology is? It's not really about how long you're going to have that weapon to yourself, but the operational experience through wars, training, war games, upgrades and general usage that is invaluable. Stealth operations have been going on in the USA since 1980's. Russia hasn't produced a operational model yet. Doctrines take time to form. You can't copy that shit beyond a rudimentary level.
China proved this exact point when buying a non combat carrier specifically for training.
Russia is 100% likely to run into production problems. It's not easy producing a fifth generation plane. Especially, when you don't produce anything for 5 years. What happens if Russia's engine gets delayed? Or infinite possibilities that can go wrong when skipping all the experience. So far Russia hasn't produced a single clean sheet aircraft design since the Soviets.
Remember, those scary stories about the stealth bombers Russia was going to produce? They ended up producing more T-160's. All their promised naval upgrades amounted to nothing. I'm supposed to believe Russia has somehow produced a wunderwaffe?
Give me a break. Russia is overrated. Hangover from the Soviet Union.