It should be enough to play BF3. It may not be enough to max the settings, but you'll get some of the best visual quality available on laptops today. However, that is 100% guesswork since we don't even have a demo yet.
Unfortunately, the GPU isn't upgradable, but if you're not worried about voiding your warranty you could always carefully repaste the GPU with higher performance thermal compound like GC-Extreme (my personal choice for desktop GPUs) or IC Diamond (lots of others swear by this stuff, but it is a bit abrasive). Then, with the repasted GPU you could use MSI Afterburner or EVGA Precision to overclock the GPU to get a bit more performance out of it.
Again, since we won't know how our G73JWs will perform until the game comes out, I'd hold off on doing anything drastic. I haven't run into any games that it can't run full out without any trouble, so I'd exercise patience and see what comes down the pipe from EA/DICE first.
