Again, it's nothing more than some news articles twisted and abused into falsehood.
Just a few things derail the argument:
1. The Sagittarius Elliptical Dwarf is largely in one piece (with a few star streamers) and currently positioned on the far side of the Milky Way, as it makes another trip around. the streamers have not shown to be the cause of our Sun.
2. I subscribe to astronomy magazines and keep up to date with astronomy news. If even the slightest chance existed of this to be true, I would have known about it.
3. No mention of it: http://www.solstation.com/x-objects/sag-deg.htm
4. Enough said: http://astsun.astro.virginia.edu/~mfs4n/sgr/