Not necessarily, there has always been a next version in every Fighter design. Its not like when a design is moved to production, the sceintist are exhausted with ideas on improvments on the older desing and they have to start from scrap
Would you say the F-15 Silent Eagle is a 'stealth' aircraft? Not necessarily. For an aircraft to be 'stealth', it has to be designed from scratch.
Actually, it may even be possible to make an SU-30 'stealthier' by key modifications. Modifications can be, use of composite materials, retractable weapons, removal of canards, etc. But certainly not 'stealth' in the entire sense. The F-117 set that benchmark a long time ago. And now we see the F-22 and soon the F-35. As far as the Russians go, there would be the T-50 and the Indo-Russ FGFA of yours
But nevertheless, the MiG-35 sounds good, but certainly not as advanced as the F-35. Especially as far as avionics go. Let alone being 'stealthy'. The MiG-35 lacks the shaping, and retractable weapons.
And of-course let's not forget, the engine - the most important and most difficult part of any 5th generation aircraft, or any aircraft for that matter. The Americans are pretty thorough on that one.
If they want to compare the MiG-35 to anything, compare it to the Rafale, EFT or something. And guess what, those two beat the MiG-35 during India's MMRCA competition.
Just because they are both named "something" 35 doesn't mean that they are equal in terms of capabilities.
The F-35 is a generation ahead... enough said.
That was funny