LOL apparently it was Deino who debunked it:
it is interesting to see, i do not know the degree of reliability of the rumor T-5-6 has flown, Rostec has not reported yet anything, same Sputnik news or RT, the reports come from posters of Airforce.ru.
As time passes we will understand why, if in 2-3 weeks they do not post pictures of T-50-6 in websites like which by the way posted a new picture of T-50-1 see link
you can see it was a rumor and that will explain why Rostec and Sputnik news have not report it.
when they post T-50-6 pictures and release its first flight date we will now how reliable was that date, but it seems it was just a rumor, but who knows still can be true but i doubt it