So, as stated in the last blog, we've put a lot of work and research and thought into cross bikes and disc brakes. It's a complicated subject, for sure, with a lot of moving parts and pieces. A lot of the moving parts are primarily related to frames: that's where the spacing issue is, and it's primarily an "either/or" fitment on carbon bikes. But it's also parts related - disc specific tubulars aren't readily available, you're still limited to mechanical discs (or one of those unattractive hydro converting things), etc. How all of these things shake out, and whether they add up to a switch that people want to make, is still unknown.
Fortunately, this is one of the rare situations where you can be a little bit pregnant. We're offering our HOT BUNS fork with either canti brake studs or disc posts. Or you can get both forks, but you have to pay extra for that ($200). Fundamentally, they're the same fork - similar weight, similar layup (except as dictated by local reinforcement for mounting parts), same mold shape, same all carbon 1-1/8" to 1-1/2" tapered steerer (it will work on lots of bikes out there), yadda yadda yadda. We've been sort of keeping this option in our back pockets, but we're going ahead with it. It makes a lot of sense and offers a lot of benefit, so read on.
Here's the deal. If there's a more important brake on your bike (and there is), it's the front one. There's a reason why mountain bikes often use bigger rotors on the front wheel than the back - the front brake sees more load and works harder, and you benefit from the increased modulation available from a brake with greater overall power. There's probably not a ton of difference in mud clearance benefit that a disc in the front offers versus one in the rear (except as I'll talk about below), but from the little bit we've seen of discs on the track in top level competition so far (which basically amounts to what Tim Johnson has done) the deal isn't clearance anyway. In muddy races, Johnson is taking a clean bike from the pit as often as anyone else, the story has been that his braking stays better between pits.
Swapping one fork for another is logistically and functionally pretty easy. Fork spacing is 100mm and it's going to stay that way - mountain bikes are at 100mm, road bikes are at 100mm, and cross bikes are at 100mm. You aren't going to buy a 100mm disc wheel this year and have it be useless next year. You can buy a disc hub wheel and use it with cantis indefinitely (I had disc compatible wheels on my mountain bike long before I had disc brakes). If your wife has a canti bike and you have a disc bike, you can swap front wheels back and forth between bikes. No sweat.
With the frame, swapping back and forth ain't so easy. The big reason is hub spacing. You get a bike with discs, you're going to want 135mm spacing. That means you can't use your road wheels for cx even if you are set up for cantis. There's no middle ground.
There's also a frame design element. You're compromising the function of both to create a frame that can do both. When you add discs to a bike, you need to add a bunch of beef to the non-drive side and obviously have the local reinforcement and fitment for the brake mount itself. To keep the canti studs, you need to keep the weight of reinforcing the frame where they go, you need to have the studs there (not so fun to hit with your leg on a dismount/remount, either), and you need to keep the seatstays pinched together enough to allow the cantis to reach the rim from the studs - you don't get the benefit of really wide spaced seat stays and the mud clearance that would provide.
So if the great cross brakes debate has you feeling confused, cheer up. We can help.
Will the frameset and bike have the disc or canti option? Or will the disc CX fork only be available separately?
Sean, on both the frame and the complete bike you can choose either the disc or canti fork, or for $200 more you can get both. If you go with the disc fork on the complete bike we use an Avid BB7 brake instead of the Shorty Ultimate (which we do still use on the back).