As having Gröna Lund as my home park I'm VERY excited, looks better and better the more I get to see of it. And believe me, this does wonders to the park's skyline.
I just wanted to add that the new coaster you're talking about is probably the plans to enlarge the park over a nearby parking lot. The proposals for the area are all clear and approved and the area is believed to be opened in about 2-3 seasons.
EDIT: I would show you a picture of an early rendering, but I can't link to it since it says I've to be a member for 7 days before I can do so even though I've been a member here since more than a year back.