Not normal. Given the angle of your photo, I can't tell if the cup has worked its way out of the frame (not something I've ever seen) or the top cap has migrated. Do you have play in the system that you can feel by pick up on the bars with the front brake applied?
I'd pull it apart and inspect it to ensure all is good. Often there are thin washers installed between the cap and the top headset split ring to space the cap upward so it doesn't rub on the frame. Too many will produce a bigger gap.
Wow, I'm pretty impressed. I just got this email within an hour of my inquiry:
Thanks for reaching out. I'm happy to hear that you love your Stumpjumper ST29 alloy. The gap between the bearing cover and head-tube is totally normal, as long as you don't have any play and the headset moves freely then you're bike is totally fine. I hope that this info is helpful and that you're out ripping the trails on your Stumpjumper.
A forum community dedicated to Mountain Bike owners and enthusiasts. Come join the discussion about bike parts, components, deals, performance, modifications, classifieds, trails, troubleshooting, maintenance, and more!