>>5239204http://www.fastcoexist.com/3048017/why-lego-is-spending-millions-to-ditch-oil-based-plasticThey look for reducing the CO2 emission caused by using ABS, that's it - and it's a long term plan anyway, seems like they want to reach the goal in 2030 if not later.
They explicitly state the new material would have to be able to withstand all ABS does, hence it'd be weird if it would just "dissolve after a few years". You probably just minsinterpeted the part about recycling which has nothing to do with the product dissolving, it just means that the new material would have to be easier to recycle in normal recycling facilities since right now Lego largely has to recycle it on their own, that's all. In general, no reason to worry.