From 1991 untill 2006 the modernization of T-72's was provided up to the T-72M1 level(look its spec). It has 1st gen IR device, K-5 ERA and its armor and IR suited in raw M1 Abrams level (see oficially info of NII Stali about it).
Starting from 2006 the new variant of modernisation was born with new gen IR TV imaging device, Relict ERA, new engine, auxulary energy supply, termal sensor muzzle reference system, more precise gun, longer autoloader, stronger munition, IR/Radar signature reduce measures etc etc under the name T-72BM. This model became the answer to M1A2 Abrams.
On the pictures:
1) T-72M1 specs
2)-4) T-72M1
5)-6) T-72BM
: Look, if you have a fleet of 25 000 tanks & between them some 15 000 well upgradable T-80's T-72's and T-90's, u are in total stupidness if u start mass production of brand-new tank without thinking about what you have allready. And if you are thinking about a new caliber (not mention 135 or 140mm) for ur new gen tank, so why you dont better think about new caliber for all ur fleet? Otherwise, you will remain with only few handreds contemporal tanks and 10 000 rubbish pots with much logistic headache. I'm used to think, the modernisation (if availiable) is the most effective way to rise the military potential. Yeah, Russia keep run for some 50 new tanks a year, but some 150 additional are upgraded. I think, this relation will be kept when instead the T-90's they would roll out T-95.