There will be ladder resets! But, it won't come in the form that we are used to. The ladder resets will happen when a new expansion pack is released. Every xpac will bring a level cap increase, making old gear not as desirable as xpac gear.
It won't be a hard reset like we are used to - we will not have to roll new characters in order to participate in the new ladder, but all the existing characters will need new gear that will come with every level cap increase. The result of this will be a continual decrease in demand for items that aren't at the level cap, but a poignant increase for items that are at the cap, because there will be more chars demanding better items then d2 ever had. This will keep the economy in check. Items naturally decay in value, the stimulant is the infusion of new items - ladder resets create new demand by creating scarcity, the exact same thing will happen when the level cap increases.
The system in d2 was far from perfect, it was an evolution of an economic system which had no base to begin with. When the only option to stabilize an economy is by destroying it and starting fresh that should set alarm bells going off. It sucks to admit, but the system was so broke before that it is hard to imagine one where a free market can actually take place.
(this is assuming that xpacs bring an increase in the level cap, which I'm pretty sure will be the case)