If they had the rubles to build a new plane and this is it ready for purchase at MAKS21... I hope a lot of countries took their cheque books, but why would they be hyping it like this if it was already ready.
This roll out under a tarp was done with the Su-57 in 2009 for a taxi, it didn't take off till a year or two later and is only entering service now... a decade later.