I looked at the Nexus 4, it is a very nice phone. But I was put off by the glass backside, too much potential for breakage. I think the advantages over the Gnex are clear but not enough to warrant a new phone purchase so soon. I knew before I even saw it, that there would only be a tiny chance I would buy one of those.
When the Nexus 5 comes out I will be checking it out with great interest. As of right now, I'd say it's 50/50 if I will get one. I also want to start developing for multiple platforms, so I may put my money into a BB10, or a WP8. Especially since the Gnex is supposed to get Key Lime Pie, I'll still have access to the latest Android without needing to upgrade hardware. It's really big a wait and see game for me right now.