I was really starting to like those guards, but if they're working for L, then they're dead to me.
I don't care what L's intentions are. Someone who kills anyone that disagrees with them, or even learns about them, is a top tier villain. Don't care how goofy, quirky, cool, or good looking they end up being portrayed when they're revealed, whatever end they get is going to be too good for them.
Also, I think with this chapter we can rule out Lily being L. If these two are working for L, then their conversation with Lily in the hallway a little while back doesn't make any sense.