I doubt that would be a problem.Unlike some people in this thread, I can see these chips at high enough clock speeds being very attractive alternatives to more expensive lower clocked quads. My only concern would be potential problems with multi-threaded software working optimally on a 3-core cpu since I'm sure nobody designed the software with anything but multiples of 2 in mind.
Many people don't know that quad-socket and higher socket systems have been available for over a decade, way before quad or dual-core processors were being designed. I own an ALR Revolution 6X6 which is a hex socket-8 dating from the mid-late 90s. I can add any number of processors from 1 through 6, odd or even, I like and the system works fine. If software took advantage of any combination of 'cores' way back then, it shouldn't be a problem now.