lifted from salsa blog;
Option 1: End Cap Swap & Wheel Dish
This option is only intended for wheels with Salsa Fat Conversion front hubs and rims with 12.5mm or less spoke hole offset. (NOTE: This includes the stock front wheel.) The Salsa Fat Conversion front hub is convertible from 9 x 135mm quick-release to 15 x 150mm thru-axle by changing the end caps. Salsa will have these end caps available around the same time the fork is. The end cap swap keeps the brake mounting surface aligned properly with Bluto, shifting the hub to the left side of the frame/fork centerline. In order to keep the rim and tire centered in the frame, the wheel must then be re-dished 7.5mm to the drive side. Warning - This option cannot be used for Surly Clown Shoe rims, or any other rim with spoke hole offsets larger than 12.5mm that is laced to a Salsa Fat Conversion front hub. The re-dish yields poor bracing angle of the spokes on the right flange and can result in an unstable wheel.
Option 2: New Hub or Front Wheel
Salsa is offering a 15 x 150mm Fat Conversion front hub compatible with Bluto and it will be available at the same time the forks are. This option is best for people who want to use rims with larger than 12.5mm offset spoke holes (like Surly Clown Shoe), or people who don't want to bother with Option 1 above. This option also results in a better tension-balanced wheel build.