I was actually going to post this myself but in a thread I'd title "Deep Sleepers." I don't see Thomas "beating out" Harris yet, and there's some mild politics involved. But Harris is a very average LB and I think the Chiefs would rather see if they have anything in Thomas, whom they like. If not, add MLB to the list of needs for the 2009 offseason.
Definitely worth keeping an eye open for and shouldn't be dismissed.

This may end up being Herm sending a message to Harris. Ideally I believe they want to keep the linebackers the same as last year, but with Harris performing better. This may be do or die for Harris here.
I'm reading the Demorrio signing as more of a long term move now. Edwards is older. I think he's at least 35. Harris hasn't showed anything to speak of. So having him around as a safety net for this year and a starter for next makes sense to me.
In any regard now is the time to see if you have a player in Thomas. You have nothing to lose.