Lets face it arjun design is a dead end,it lacks development potential for future.
For future we need 55 ton approx tank with smoothbore cannon,3 crew,no gap in frontal turret,might even be unmanned,secure ammo compartment as well as the ability to field a big gun with long rod APFSDS round.
Arjun has allowed us to develop many key armour technologies which will be incorporated in FMBT.It can still deal relatively easily with paki tanks,but its not the mass produced tank of the future .
Arjun has allowed us to develop indigeneous NERA,Kanchan composite armour,automatic target tracking,navigation system,suspension,panaromic sight,weight reduction measures,and set in motion development of new 1500 HP engine.
But we need bharat forge/drdo to build a new tank gun .If necessary we can do it like turks and get tech from south korea.