Ancient stuff can be revived if it's a good and timeless in design. Recently China started making Tu-16s and An-12s again as the H-6 and Y-8. But not all old stuff is good.
One of the problems is the maintenance of the variable wing. Russian jets are not known for serviceability, reliability and technical support. Add something complex like this, and you risk buying a lot of white elephants.
Then the Tu-22M3s being offered are all second hand. PLA don't like buying hand me downs unless its something they want to take apart and study. There is doubt that Russia could build new Tu-22M3s from scratch because of parts that may need to be sourced from former Soviet republics---they could not fulfill the IL-76 order already, and had problems making the new Sovremannies before.
The Su-27 maybe dated design but when the Chinese bought them, the particular airframes are brand new. China is making brand new Su-27s. The H-6s are brand new. So are the Y-8s.
Trying to sell used aircraft isn't going to work. The only way I think China will fly the Tu-22M3 in PLAAF colors is either when the Russians could manufacture them brand new, or license them to China to manufacture them brand new.