Obviously, the best indicator will be the track record after it has been on the wrists of many people for six months. But there is no need to speculate about durability design changes. I'll spell it out for you. The primary problem reported by v1 users here was corrosion on the charging plate which was on the inside of the band, touching the skin in v1. This version has it where there is no contact with the skin. (Durability improvement #1.) In fact the only metal touching the skin appears to be stainless (Durability improvement #2.) Another frequent problem was the number of scratches common on the display. This had two causes. First, the TFT display was a scratch magnet. That has been replaced with an AMOLED display with Gorilla Glass 3, which is unlikely to scratch easily. (Durability improvement #3.) The other contributing factor to scratches was the thickness of the band, esp the ends of the flat display, which sticks out so far it is easy to snag on anything near one's wrist. That has been improved by the curved display (Durability improvement #4.) Another problem with band 1 was the battery cover coming off. I believe that a contributing factor was the lack of flex in the band. Just putting it on or taking it off was putting pressure on any weak point. This version has far more flex, which should minimize the pressure on any one point. (Durability improvement #5.)
I would conclude that durability improvement was a primary objective for MS with this version.