The para 3 is definitely not a replacement marketing thing, like an upgraded model. With the 3" blade it broadens the marketability of the para series for gents like myself that are "encouraged" to carry 3" or under knives by certain laws, city ordinances in my case so traveling with a larger knife can be questionable as the state law is pretty relaxed but the cities in the metro area are pretty widespread in what they allow so you have to plan for the tightest law you'll be working in.
I would be more worried about the sage 5 going away from the para 3 than the para 2 going away, if you're a sage knife lover.