Actually, by the rules, we know we will face one, and only one (at least assigned) of the three teams we just beat. Of the three, which is most likely?
There are 3 other forts, and no team stays in the same fort.
By the rules we will face a mix of squads that haven't worked together this event, and be matched up with two other squads from two of the other red teams. This is of course provided that we haven't beaten the snot out of literally everyone and caused them to drop out due to the injuries we've inflicted upon them.
Now, as far as our opposition goes... there's two tacts they could take here. The first is that Mist expected us to lose the first round badly, or at least not be able to score points. They did put us up against a team that was very strong for defense - Team Kurenai for the Byakugan and other tracking elements to see us coming, Hazama's team to give them the Lightning Pillar jutsu, and Team Downfall to give them Wakahisa reserves, trap making expertise, and extra insight into us. With this tact, they would put us up against a more normal team next round to make it not look like they're being too hard on us.
The second option is that they want to screw us next round too, not caring what it looks like, in which case I expect the
intended plan is to put us up against squads from Waterfall, Hot Springs, and Rock, which would be a nightmare combination to defend against. The invisibility bloodline would allow them a stealth option, with Blood Clones allowing for good scouting options and the Minawa reserves to help them keep using jutsu, and the top Rock team has a bunch of Earth jutsu to allow for scouting and demolitions. Now, I put emphasis on the word
intended here, because we may well throw a wrench in it by doing well here today and inflicting Moderate Consequences on enough people that they'll drop out.
Unfortunately, some of the people in these groups have a good chance of some of their members escaping today's rampage. The invisible girl can escape due to being invisible and assuredly a stealth specialist, unless we're really lucky in catching her. The Kotsuzui bloodhound kid apparently can heal absurdly fast, which means that even if we get him with Moderate Consequences today he might actually have healed in time for Round 2, and the Namazu on the Rock team could potentially escape with Hiding Like a Mole. IMO with this combination we're likely going to want to go on a more aggressive defense strategy for Round 2, attacking them as soon as their two hours of planning time is up.
EDIT - though it should also be kept in mind that Mist would want some of these teams eliminated as well as us, if not as much. They do need to ensure some of their own genin get into the tournament, and keeping three top scoring teams together next round doesn't help with that.