I run a GTX 590 with 1.5GB of vRAM, as well as an i7 2600k @4.4ghz and 8gb of RAM.

I'm wondering if you guys think the 1.5GB of VRAM I have will be enough for the full version of the game (single player, etc.), at 1680x1050, limited to 45 fps, when it comes out.

I know this game is pretty hungry for VRAM and I've only got 1.5GB, but I'll only be running the game at 1680x1050 and limiting the frame rate to 45 fps to avoid annoying frame rate drops

I'm also planning on lowering the following graphical settings:
Particle effects - medium
Game effects - High
Objects detail - High
Antialiasing - SMAA 1x

Thanks in advance.

Yes. I'm running TriSLI 680's @ 1080, and it doesnt seem to go above about 1600MB on average. So at your lower res, with lower settings, of course.

You should see 70+fps with what you are describing.