Most countries in the world are still using so called "old
tank", for example IDF just recently retired their own Centurion
and still have many M60( upgraded of course) in svc.
Most important is whether these so called old tank are upgraded to
perform in modern warfare especially against their perceived
threats.
The most modern tanks in SEA other than what SAF have is the PT-91
which is a actually an upgraded T-72M1( 30 y.o. tanks), so any old
tank with proper upgraded FCS, armour, powerpack etc , a old hull
could still performed, that is why there are still so many "old
tank"around in most armies.
Having a new tank in any armed forces is no easy task especially a
large qty, let's say qty of 300 tanks, the army will need to train
at least 300 set of crews, large group of maintenance specialists,
instructors, logistics etc.
Then there is cost incurred above plus the actual cost of modern
tank, a light tank today could easily cost at least USD2mil, if
it's include modern FCS with TI, BMS , composite armour, APS etc,
it could be as high as USD3~5mils!!!!
Therefore it is very large investment and it is not simple decision
to make especially when it will be used for at least 2~3
decades.
Lastly, there is this notion that some believe that tanks are
obsolete becos of modern land based ATGM, precision ATGM from
attack helos and fighters etc, some army are actually moving away
from having any tanks and instead using low cost wheeled fire
support AFV etc.
That is becos it was well demontrated in GW1, where most of the
Iraqi armour were actually decimated by fighters and attack helo,
way b4 the actual ground war started.
For example the Apaches itself destroyed 800 vehicles including 500
AFVs!!!
One thing tank for fire support role, tank is still needed, but for
tank vs tank senario, is it still neccessary????
I dunno, becos with longer range ATGM as compare with tanks, attack
helo etc, it could still decimated a large armoured force, that is
why the SAF Gen was saying last year that SAF might be looking
having a light tank replacement using missile only , instead of a
tank gun!!!