Breaking Down the Shoot Out / Last Scene
To refresh here is a link to the ending: 
Ok, so I was a little off set by the ending because the Russian guy with the head tattoos opens fire on the group first and he has what appears to be a semi-automatic/ if not automatic rifle. Now realistically, he would be able to kill or at least shoot the whole group pretty easily.
Now there are only 4 people in Arvo's Russian group in the scene, one of which is an unarmed Arvo. That means that hypothetically we have the advantage here. (Mike, Bonnie, Clem, Kenny, Luke = 5) ALL of which are armed. So technically we have a huge upper hand having it be 5 on 3. However, Luke is completely off put by the shooting of Rebecca. So if Telltale is going to play this thing exactly from where it left off, Luke might need an extra second or two to regain his sights.
Now as for who is pointing at who and their weapon:
The russian guy with the tattoos (semi- automatic weapon) is aiming at Kenny (pistol) and vice versa. BUT Mike is also in range.
Mike (pistol) is aiming at the guy in the back (shotgun) and vice versa
Bonnie (pistol) and the Russian chick (pistol) are aiming at each other
Luke (semi-automatic or automatic) is aiming at Arvo (unarmed).
The player will likely determine Clems first actions.
Now based upon the above, and the man with the tattoo opening up fire first I would guess (and this sucks for me to say because he is my favorite character left) Mike is a goner in this fire fight. He also has the shotgun guy aiming at him that clearly overpowers his pistol.
I assume since Arvo is unarmed, Luke will start shooting at the russian guy with tattoos.
All in all I say the group escapes with just one casualty (my guess is Mike... well I guess two if you count Rebecca) and every member of Arvos group is killed besides Arvo. Than you will have to decide what to do with him.
Please let me know if I am in-correct in anything and I will edit the post. Also please add your own findings and predictions.
Comments
If you chose to call for help or do nothing when faced with a reanimated Rebecca, Kenny turns and takes the shot, but if you do nothing, Bonnie is the one who warns Kenny, so one or both of them would be a bit distracted.
Yes I was going to mention this. In my play through, I called for help because I wasn't 100% sure Rebecca was animated yet. I thought she just might have been really sick. I called for help and Kenny walked up and shot her. In this instance, Kenny would be right in the line of fire for the russian guy with the tattoos on his head, and I mean like right in his aim.
I think that's how shooting rebecca will matter. If you shot Rebecca, you won't have the necessary bullet to protect someone else, and if Kenny shot rebecca, he won't have the necessary bullet to protect himself.
Keep in mind you also have the two bullets on hand that you found from the Walker Jane told you to search. Could be a key part.
Aha!
And a nail file (if you took it) . . . not sure how good Clems knife throwing skills are but ya never know!
I can't help but think the tattooed guy was aiming at Luke in that scene. Mike was more to the tattooed guys right then where he was aiming. I don't think I heard a shotgun go off, so Mike might of got a shot off first and hearing the shots, Bonnie might of shot the girl. Leaving just Arvo, and the tattooed guy.
Yea, I was going to get into the gun shots and originally i thought it is not a good sign as you hear the shot from the russian guys gun multiple times but then I figured Telltale is just using the same sound for multiple guns.
Assuming Clem will go to protect the baby first, hopefully she can get a good shot at the russian guy with the tattoos. Her size could play an advantage here.
Luke in both cases I believe is the one who completely turns away from Arvo to look at rebecca. He could be shell shocked since now very member from the Cabin group has died.
If you're interested in perhaps viewing a more detailed thread and/or discussing this with someone else who is also really interested, you could check out this thread that @Legendary12 created. He posted up pictures of all the character positions to help out with the scenario.
Anyway, at the end Luke isn't aiming at anyone because he takes a moment to turn around and shout "No" so he's out of the gunfight for now. You couldn't assume he's going to aim at Arvo once he gets his bearings straight. If he was smart (which he is) he would try to take out Burich (the boss with the AK) or Vitali (the thug with the shotgun).
You also have to remember that shotguns have a spread on them so Mike isn't the only one that is in range of the gun.