Well, that is it isn't it??? In order to take down the Saviors they are going to need numbers and weapons..
While the number of guns this group had was limited, it is a large group and thus gives Rick what he has been looking for the last couple of weeks... Numbers to attack with.
My

on how Carol, Morgan and the Kingdom comes into play...
Someone from the Kingdom that matters to the King, and in the end to Carol & Morgan, is going to get killed. Although losing Richard would be a shock, I don't think that would be enough.. So who is left?? The Kid..
The King feels fully responsible for his parents deaths and so has "adopted" him... Morgan has taken the kid under his wings to train and teach.. Carol so far only had one run in with him, but showed enough "compassion" to teach him how to handle himself in the woods..
Thus, I think the Kid gets killed in a couple of weeks, sending The King, Morgan and Carol into a full out rage to get revenge.