I have a faint hot spot when I use my Olympus 12-40 f/2.8 pro lens on my G1. It is noticible on the raw file, but when I'm finished processing, you don't see it. It is more of a loss of contrast, and only a bit of extra luminosity.
Since the coatings inside a lens can give off IR and cause the hot spot, I imagine that the amount of bright sun would make a difference in the spot effect. If you are not seeing it, I would not worry about it. I will be getting that 16-50mm kit lens in about a week, and I'll try it out on my NEX7 665nm, and let you know if I see it or not in my photos.