Samsung has nothing to do with the Galaxy Nexus, it is a Google device. The Galaxy Nexus, GSM version, has been on Jelly Bean for quite some time now. The problem is, Verizon and Sprint have to do their testing and own updates, which slows down the update processes. Verizon is pretty famous for being late to update parties, and Sprint isn't much better (if any).
If the SGS3 is getting Jelly Bean soon, I would bet the Sprint and Verizon versions are left out for a bit. Verizon doesn't care about the Galaxy Nexus, as it makes very little money on it due to very few built in Verizon apps. Other devices come with all sorts of Verizon bloatware, stores, maps, and other stuff that potentially makes them money.