I'm about to slap 700c wheels and 700x35c cyclocross tires on a Scott Reflex mtb that originally came with 26" wheels. Disc brakes make the job easier. I checked frame clearance and there's no problem for tires up to size 700x37 or 700x40.

The resulting higher BB brings no adverse consequences, according to Dave Moulton's ideas, among others.

But changing the outer diameter of the tire will change fork trail. I'm waiting to try it out but I've still gotta build up the rear wheel first.