A common turret built around the T-90s 2A46 gun, DRDO sights + FCS and the already fully-indigenized V-92S2 engine can be used to standardize both fleets, simplify logistics and perhaps even obviate the need for FRCV (with add-on modular armour packages) until FMBT is ready. T-90 Mk3 is more of obsolescence-management than an upgrade, imo.
That opportunity is gone. More like the army rejected it.
Now the plan is to get new upgrades in and export them as and when they are replaced by FRCV.