The sad thing is, there is a concept model for an aircraft Mig designed that was to be a replacement for a mig 21. It was a single engine design, and whilst I doubt it would have proven as effective as a mig29, it would have been cheaper and easier to maintain.
Thats not knocking the Mig29, im a distinct enthusiast, but I think Mig kind of designed themselves into a corner with it a bit.
Though they hardly could have foreseen the end of demand for affordable fighters, both for the USSR itself and its clients, which occurred with the end of the Cold War.
JF-17 is an excellent example of this sort of cheap but still ok fighter aircraft (and Mig consulted on this design, btw) but it has not got very many customers. Here is a nice pic:
Yes, thats really quite a nice fighter indeed. I think to be honest Russia could do far worse than load up on them.
Im not knocking Su57. I think fully matured it would be a fine fighter indeed. What I personally doubt is that Russia has the money to mature it to the level it will need to compete with F35. Which surely it will need to out-compete judging by how few Russia is planning to buy of them. If you want a model of what I see happening its the EE lighting. Worldbeating when new, the Government never had the money to mature it to the level it required. But that didnt stop them keeping it in service for the next 30 years.
Russia has new design's for aircraft, tanks and missiles coming out of its ears. Its easy to throw cash into prototyping some new machines, its entirely enough to start stocking up on them in more than trace elements. And enough to keep upgrading them to keep them current.
Like I say, time will tell. I hope Im wrong because its a fine looking aircraft.