Features get rejected all the time, even some pretty substantial ones. That said I think there's two things to keep in mind: 1. If someone is willing to take t

Features get rejected all the time, even some pretty substantial ones. That said I think there's two things to keep in mind: 1. If someone is willing to take the time to develop and submit something to the kernel, it probably has some redeeming factors to it. The original idea or code might not get merged, but something similar to meet those needs likely can be if it's really something the kernel can't do. 2. The modularity of the Linux Kernel build system means that adding new features doesn't have to be that big of a deal, since anybody who doesn't want them can just choose not to compile them in. It's not always that simple, but for a lot of the added features it is.