Companies are in business to make a profit. What would be better for them than having millions of their previous products made useless and a new market for millions of new product created with the stroke of a pen. I'd bet some of the larger high capacity magazine makers are already jumping up and down for joy and having preliminary meetings to discuss the new gold rush for them. Magazines do not take the level of re-tooling for manufacturing as does items more complex
Actually quite the contrary. I would not be surprised if alot of these companies refuse to go through the expensive process of having to tool up to make 7 rd mags. It's not a simple process and it can be very expensive. Also, considering only NY has this ban, and considering NY makes up a small percentage of firearm sales throughout the country, they might not even bother. The cost vs benefit might not add up to make specialized mags for only one state, especially when that state has such a low percentage of firearm purchases compared to others.