Now the final X3 won't be exactly like the xActivity. What it will have is the styling cues from the xActivity like the angular lines. If you remember the BMW CS1 concept you notice the new Z4 has a lot of similarities with the CS1. The lines etc. If you consider the latest models coming from BMW, the Z4 and new 7 series, you'll realize that upcoming BMW designs are going to be pretty wild and wacky compared to past years.
Like the xActivity concept, the X3 will be more wagon-like than X5-like. This is not surprising considering the X3 will pretty much be a 3-series wagon on steroids.