The operating system will be Android Lollipop and the interface will be one made by Samsung itself. However, the good news is that Samsung gives up to many of its applications that came pre-installed on Galaxy phones (and other models). Finally, you must know that Samsung will rely on wireless charging more than it ever did before.
The first smartphone to feature a wireless charger was the Palm Pre, a resounding failure of the company, but it was done in 2009. First time Samsung tried it, they integrated it in Galaxy S4, but with a special battery cover. Now everything is integrated in Galaxy S6 charging mechanism, and the component that goes into a socket comes into the box. The fact is, that neither 2015 will be the year of the wireless charging but more like a marketing strategy to increase the interest.