You probably have enough to go on, but I was just in a similar boat and figured I'd share my $.02
The Samsung GNex is still, even compared to the GS3, a very good phone. Yes, the S4 processors are monsters, but the GNex still has a dual-core processor and 1GB of RAM. If, like me, you have plans to "modify" the phone (rooting, overclocking), it's even better.
Now, that rumored LG device sounds great (4.7" IPS, HD display, quad-core S4, 2GB of RAM) it's still from LG (which is a big time downer for me).
On top of that, we're just breaking into the quad-core technology, and Motorola is the only manufacturer so far to create a quality battery (RAZR Maxx).
So by my thought process, buying the GNex now for $350 gives me an incredibly flexible device, beautiful HD display, and, of course, vanilla Android. The S4 dual core processors aren't enough to sway me to another device, so I plan on hanging on to my GNex for another year, then reevaluating the market. I expect more power conservative quad-core CPU's and bigger, more efficient batteries.
So as beautiful as that LG device sounds to me, it doesn't sound beautiful enough to warrant a price hike or beautiful enough to lure me from a quality Samsung device to an LG device. Sure, the GNex may be beaten by the next Nexus, S3, One X+, and RAZR HD, but it's still a competitive phone, and that's enough for me.
I'm a college kid, so having a Galaxy Nexus with unlimited everything (Straight Talk) is a wonderful privilege, and I saw no reason to overextend myself for the higher end devices, or inconvenience myself to wait for a rumored Nexus device.
I'm very pleased.