LaGuerta was secretly tracking Estrada in order to catch Dexter, so her showing up alone makes sense. Estrada was bait for Dexter.
The thing that bothers me is the guns used...
LaGuerta gun was used on Estrada, Estradas gun was suppose to be used on LaGuerta but Deb shows up. Deb uses her gun on LaGuerta instead, so how do they explain that? Plus, the trajectory of the bullet fired etc...
I don't see how this will play out correctly in Dexters favor.
Now, I think Angel will catch on. Matthews might or might not get involved as well, I'm still unsure if he planned for Dexter to take out LaGuerta (knowing that Dex is the BHB), or he truly thought he isn't.
Does Deb take LaGuertas spot? Therefore promoting Angel to Lt, stopping him from leaving? Or does Matthews step back in?