eckherl, I am just trying to come up with some numers, lets see now,
Indian Army has 63 armoured regiments, each regiment comprising of brick of 62 tanks (45 for combat 17 for training, Attrition and replacement etc)
As of today these comprise of,
T90S - 5 regiments (@62 each - 310 total)
T72M1 - 35 Regiments (@ 55 each - 1950 total, lower than required bricks)
T-55 - 10 regiments (@55 each - 550 in total - Modernized)
Vijayantha - 11 regiments (@72 each - 790 in total - modernized)
Reserves - T-55 - 200 Vijayantha - 1000
Now lets look at the modernization plan
T-90S- 310+1000+347 - Total of 1657 - 27 Regiments, T-90S will replace all T-55 and Vijayantha (Modernized) which will move to Reserves.
T-72M1- Now here is the confusion How many will be modernized? A recent report indicates India signed a deal with Bumar of Poland for 1000 tank engines. Lets assume all 1950 will be modernized.
So total - 1657+1950=3607 = 58 Regiments (Assuming full brick of 62 tanks).
That leaves 5 regiments short, 124 Arjuns on order make 2 regiments, so worst case scenario, we should expect order for 3 more regiments of Arjun. That comes to Total of 310 Arjun.
If we assume all T-72s will not be modernized, then we can expect more order for Arjun.
By 2020, even the modernized T-72's will be one their out, so that's where Arjun Mk2 will come in.
I know, lot of assumption, but that is the starting point for a debate.