ProtegeManiac
Headphoneus Supremus
The problem then is that you still need boots on the ground, and APCs (essentially also tanks) and helicopters aren't any safer. Tanks simply changed their role, and the design and tactics are developing as necessary. From charging deep against some less-fortified positions and encirclement in WW2 (like Army Gruppe B coming out of the Ardennes) up to the 1967 Six-Day War they functioned pretty much the same way that Alexander's Companions did, and the vulnerability of tanks were already made clear just six years later in the Yom Kippur War.
But then there's still the old problem - how else do you get boots on the ground? Again, other vehicles aren't any safer, just cheaper (the reason I'd prefer the Merkava is because of the higher survival rate of the crew, not the tank). Vietnam showed that helicopters are just as vulnerable (although you can't really use tanks in the jungle), ditto the Hind's record in Afghanistan. The tank isn't absolutely obsolete, one type of tank is, as well as old tactics developed for it - the Main Battle Tank. The Merkava is the best among MBTs in terms of protection, but of course it's still an MBT; it can however make for a convincing design prospect for how a low-profile medium or light tank can be designed. Engine up front means you can still use it to charge entrenched positions not covered by helicopters with heavy missiles, while the smaller size can mean it can be easier to conceal and sneak up on targets. Instead of being escorted by APCs, they either escort larger APCs with more troops, or each tank brings its own (albeit smaller) infantry squad, reorganizing from platoons of mechanized infantry going along with heavy armor into having one unit commander-tank gunner, driver, and three or four mechanized infantry.
We're just entering another phase of the cycle that cavalry went through before thanks to pikes and guns. Guns coming into wide use didn't really make them obsolete (heck massed formations of the repeating crossbow didn't really help the Chinese against the Mongols), and pikes on their own were only useful if the Swiss were fighting a defensive battle similar to (the initial phase of) Marathon and Thermopylae;* not even tactics combining them together made all cavalry obsolete. All that became obsolete were heavy lancers,** although such cavalry were still in use past the Napoleonic Wars and even in WW1 they were still around. Speaking of WW1, just because they were useless in the Western Front thanks to all the trenches, doesn't mean they weren't useful in the East, although again these are no longer cataphracts or even riders wearing a cuirass. What were useful since the 18th Century over the Hussars and other heavy lancers were Dragoons who can get to critical points quickly, shooting from horseback or using curved swords in slashing+running attacks as opposed to a massed charge with lances, or dismounting and firing from cover behind the enemy. The Dragoons are essentially the Mechanized and Airborne (helicopter) infantry that we have now, in the same fashion that the lance-wielding heavy cavalry used to be the main battle tanks (and cataphracts were the ridiculously impractical and large tanks, like the Konigstiger).
*this one was more of ridiculous stupidity and arrogance on the part of the Hapsburgs than a revolutionary turn in warfare
**which had an even shorter reign in Japan - the massed opening charge by the heavy yari cavalry with infantry mopping up a scattered army was introduced by Shingen, then made obsolete shortly after his death at Nagashino
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In a less serious way of looking at it on the very long term, if the tank were to be really obsolete, it would probably be something that would make fighter-bombers obsolete as well, meaning a weapons platform that is fast and agile enough that conventional dog fighting tactics (and that includes long-range AA missiles) won't work since instead of trying to get behind the other jet it can just turn around and shoot it, for which its fire control system is accurate enough, and yet it has enough firepower to punch through tank armor.
I don't think we'll see such a weapon in our lifetime though.
