Near-future astronomic events that could threaten Earth
Essentially, anything could happen! We can't really predict events such as you've described.
The only event we can really be certain of is that the Sun will inevitably die in about 5 billion years. When it's almost run out of hydrogen to fuse it will expand into a red giant, becoming so large it will take out the Earth. There's a good video demonstrating this here: http://science.howstuffworks.com/life/evolution/life-on-earth-end1.htm

You could add geomagnetic reversal and gamma ray bursts to your list. Also see: http://science.howstuffworks.com/life/evolution/life-on-earth-end1.htm