All the heavy commercial engine OEM's have been factory filling with 10w30 for a few years now. Cummins, Detroit, Volvo/Mack, Paccar, all of them.
The FA-4 engines will not be out till 2017. All are on CJ-4 now and the ones already at work will only be allowed to use the new CK-4. Even then, the 2017 X15 will be in two varieties... the performance X15 and the efficient X15. How that plays out on which oil gets recommended, we'll have to wait and see. But I would suspect that they would still recommend CK-4 across the board. CK-4 can be used even in the FA-4 engines and would probably be what I would chose irregardless of OEM recommendation.
I never take OEM recommended drain intervals at face value on my commercial stuff. I always use it as a reference point, but develop my own particular intervals based on trend lines in used oil samples.