There will be however several problems with tank competition. Not in tanks but in production capabilities.
For example USA and Russia still have production capabilities and are manufacturing tanks, so they will not have any problems to fulfill any contract.
However as Russians might be willing to allow licence production and technology transfer, US might allow only licence production (or rather production of tanks in knock down kits in US and assembly of tanks in India, just like in case of Egypt) and will definetly not allow to sold tanks with their newest or best technology like DU armor.
Germany is problematic, in theory KMW and Rhinemetall due to large Leopard 2 users, have capabilities to manufacture such tanks, and are willing to sold production licence with technology transfer (look Greece, Sweden and Spain). But the question is, do they really still have manufacturing capabilities? Do Germans are willing to sold tanks to India?
France and UK are out of buisseness, both do not manufacture and probably do not have manufacturing capabilities, not to mention both don't have much tanks to be sold via second hand.
Italy same as above, + C1 Ariete is somewhat a "joke".
South Korea and Japan might offer their new tanks, but do both of them can compete whith Russia or US?
I suspect that US could offer besides tanks also full logistic support with spare weapons, spare parts, ammunition, training aids, actually US could from scrath build how logistical chain for tanks in India. Russia in theory also but due to financial problems it might be somehwat difficult for them.
Oh and there is Israel with Merkava Mk4 MBT, Namer HAPC/HIFV and Namera ARV, so if India would choose a foreing design, and it would be a Merkava Mk4, then India can buy a licence for a whole family of vehicles that shares most of it's components, reducing logistical problems. And Israelis seems to be rather cheap, high quality and willing to share technology.
Or India might follow with Arjun Mk2 but as it seems, actually not many things were upgraded, and some design solutions are... strange, and seems to not have much sense.
So if I agree that international competition might be good thing, there are things worth to be analized.