You know, I'm not sure, I'm working on a cable pattern and started the cables while doing the increases but in looking at the pattern it doesn't state what to do. I would do whatever looks the best in your opinion. My pattern is something k8, p2, k8, p2 and the cable was only in every other k8 section, so if the increases were in the smooth k8 I would have left them, but they were in the section that should become a cable, and to my leaving them smooth would have looked odd, so I cabled them.
I hope this helps,