The problem is that they are improving an active pen, which will drive up hardware costs. For WACOM technologies they improve the actual surface and use similar pens, which aren't powered.
Also, when did Microsoft stop including the pen? My Surface Pro 2 came with the pen, and in my opinion was the last point that Microsoft's Surface made real sense. The passive pens were just better. No charging, no batteries, and they just magnetized to the side of the device. Plus they were the size of real pens so they were more comfortable to use. Really WACOM's tech was better in a lot of ways. I remember when the Surface 3 Pro came out and everyone said "You don't need that kind of accuracy on a tablet" when they were talking about the 3's pen and digitizer vs the excellent WACOM system on the 2. Now Microsoft is trying to make even better pens! So... what happened to "You don't need that kind of accuracy on a tablet", eh?