Ulric has a lengthy history of using un-clanly methods to win, such as turning Mercer Valley into a minefield and suckering the Lyrans into it, or deploying Elementals to specifically headhunt officers. If he can get all the clans working using those tactics it's likely to go very poorly for ComStar.
The aftermath will be a bit worse depending on how things go.
Option 1: ComStar isn't going to hand over Terra to the clans just because they lost a bet. This I think, is more likely. The clans will be incandescent at this betrayal. Since ComStar is running administration on a great many Clan-captured worlds (The clans found it convenient to let them and did a lot of diplomacy there, which ComStar used as an opportunity to spy on them), the huge mass of Adepts in those worlds are all going on the chopping block, and the clans will almost certainly kill all their offspring as well given that's their way. ComStar runs all the communications and most of the news for the Successor Houses so they can run a massive propaganda campaign and use this to drum up support. The clans, meanwhile, are going to take off the kid gloves and fight to the knife rather than trial for things. The clans back at the Pentagon worlds are likely to get involved so Star Adder, Burrock, Coyote, etc. are all going to be sending their toumans too.
The net result will be a lot more fighting with a lot less rules. The death toll will be devastating on both sides but the Clans are the only ones with Warships and if they aren't bidding those away, they're going to be interdicting a lot of IS DropShips before they ever land to disgorge 'mechs, and wiping out a lot of bases from orbit. As the clans cut their bloody swatch towards Terra, ComStar is going to have to pull their own WarShip fleet out in a last-ditch defense which is absolutely going to raise the hackles on all the Great Houses, and also since those are going to be mostly green crews the Clans are going to beat them down messily.
Option 2: ComStar honors the trial and hands over Earth. This would actually be the best outcome, so ComStar probably won't do it. Clan Wolf probably becomes ilClan due to Ulric being the one who pulled off the win. This lasts all of a week before the other clans start trials of possession to take the title away because the clans really didn't have much of a plan beyond "Capture Terra" and none of the clans are too awful likely to decide they should just stay subordinate to Wolf. They probably make a token attempt at rebuilding the Star League but I have strong doubts the Great Houses will go for it. Due to infighting over who gets to be ilClan the clans won't do a lot of invading though there will be plenty of raids on both sides.
The clans have a fair chance of leaving ComStar in charge of the HPG network, after all ComStar's shown itself honorable and all. I actually see a fair chance of the Blakists winding up integrating into the clans (after all, they both have the goal of recreating the Star League) and ultimately altering each other. This probably derails the Jihad and from there, who knows?