Brian Schulenburg at Pass the Salt posted way back in 2007 his Top 10 Issues the Church Will Face in the Next 10 Years. Click on the link to see his elaborations, but here's the list in a nutshell:
2. Open Theism
6. Social Issues
7. Red Letter Christians
Obviously, #3 seems to be the biggest one, judging by media stories these days. However, I've been convinced for some time now that perhaps the greatest threat which the Church has been/is/will be battling is #9. And not just Jesus Junk, as Schulenburg writes, but the consumerist mindset which seems to rule the thinking of most USAmericans.
(ht: Todd Rhoades at MMI)