1.) I expect Sasuke to go through the allied forces. My reasoning for this is that Naruto did something similar when he entered the fray by going through some White Zetsu's first, showing off Kyuubi/Kurama Mode with Killer Bee before entering into the frays with the big ET baddies. I'm not saying that what Naruto does Sasuke must follow; rather, I'm just saying that there's a precedent that Kishi has set with a whopping 1 whole character, lol. xd
2.) This will not be the massive slaughter except for the the cannon fodder that people are talking about. The allied forces are composed of tiered layers of ninja ranking from cannon fodder to elite jounin like Darui (Black lightning, Storm release KG) Kitsuchi that layed his most powerful technique, that monster Earth release: Mountain Smash on Gedo Mazo
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Granted, Gedo Mazo made it through the jutsu, but powerful jutsu from people like that are going to command Sasuke's attention and Susanoo's resources. It's not just going to be the Konoha rookie's grown up and a bunch of nobodies who show up to face Sasuke. If that was the case, then it would be suicide and a strategic retreat would be necessary with some requisite sacrifices. In addition, there's Shikamaru, who by himself changes the game with his brains maxing out the abilities and masking the weaknesses of his allies while analyzing his opponents for the same. The only person alive, who's any better in the series is
currently his father because he has the experience, which Shikamaru is gaining in order to surpass him.
3.) The other extreme - people who are claiming that the regular allied forces are gonna wipe out Sasuke with ease are just screwing around as that makes no sense plot wise (Sasuke's gonna die here against allied forces like this, before Naruto and any chance at redemption or whatever? The most anticipated fight in Naruto won't happen?
Further, it's fated for him to fight Naruto at some point by both bloodline (Elder son vs. Younger son) and the elder toad sage whose already dreamt/prophesied it, assuming those "powerful eyes" referred to Sasuke's, which I feel certain that they do. It appeared Naruto did as well since he cut the Elder toad off at that point saying I know him...).
3a.) We have precedent for Sasuke's proven ability against cannon fodder. Remember his training session with Orochimaru against 100 or 1,000 (I forget which) cannon fodder ninja that Sasuke took out with ease (not a single wound) but wouldn't fatally strike (saving that for Itachi), which caused Orochimaru to remark something along the lines, "People called me a genius at my age, but Sasuke-kun has surpassed me already for that age..." That's before he even had a MS and had the CS. From here, you can say he bit off more than he could chew at the Kage summit, but it was still an impressive display as far as his performance against the Kage's bodyguards in limited exposure.
3b.) His current fighting prowess is likely far superior to where we last saw him, albeit I wonder how well he's controlled the darkness in him or if it's controlling him as was depicted in that panel at the Kage summit. Sasuke needs to find some sort of symbiotic relation with his darkness so that he can fight analytically while still being consumed by darkness, but I make no claims where he is regarding that at this point. I just hope he's regained some of his composure since his last skirmish with Team Kakashi when he was a total mess, especially screaming about Kakashi being saved by the Uchiha when he used Kamui to avoid the Susanoo arrow, oye! :shrug:
3c.) As well, the current battle conditions may be in his favor with the rain. I'm not a meteorologist, as rain clouds and thunder clouds are different, but I'd think since this isn't the Weather Channel, lol, Kishi may work Kirin in somehow with either a change in the weather to thunder clouds or Sasuke's natural use of his MS jutsu such as Ameratsu and Susanoo covered in Ameratsu, which also shoots Ameratsu arrows (lots of heat!

) to generate such clouds.
P.S. The problem is, once he engages the alliance, how does he disengage them without defeating them/losing to them, as I don't foresee that happening unless one side leaves the fight and is allowed to disengage. The alliance needs to get to Tobi for Naruto, Bee, Gai, and Kakashi. Thus, I'm not sure how Kishi's going to work it out, if there's a major engagement between the alliance and Sasuke, unless that's the main fights. Madara vs. 5 Kage, Kabuto vs. Itachi, Naruto et al. vs. Tobi, and Sasuke vs. Alliance. Something about that doesn't seem feasible from a chakra perspective, particularly Sasuke and Naruto, who then have to fight each other at some point. :shrug:
Peace 