AFAIK, Mk2 is NGMBT, so Mk3 should be a new FRCV UCP.
The Mk2 is a new 6-wheel hull with a crew capsule and an indigenous 1500HP engine, with an unmanned turret and autoloader. It will weigh 50T. We may buy a few hundred of the Mk2s as stopgap perhaps, until FRCV arrives around 2035-40, which will then replace both the T-72s and T-90s (long term).
Of 2400 T-72s, we plan to replace 1700+ T-72s with 1770 FRCV. So it's possible the remaining 600-700 will be these Arjun Mk2s, at worst split between more T-90s and this new tank. Or we will just build more tanks and boost our frontline tank strength to 4000+.
I believe Mk2 is currently moving into or is already in the CDR phase. PDR finished last year. If the engineering process starts next year or so, we could see it enter serial production well before 2030, followed by a 10 to 15-year production run for 500+ tanks or so.
Arjun Mk1A's production will end in 2028. T-90 is also licensed until 2028. Both by OFB. So I'm guessing this tank will be built by OFB as well.
FRCV is so large, expensive and complex that this tank may end up being a fallback tank in case of failure. That would avoid more imports.