When is the 710 getting released?
EDIT: I will say that, unless the price is massively lower per GB, I'd probably stick with the 510.
Reason being, performance is not likely to be 100% better. It will be better, yes, and even noticeably better, however, the question is whether it would be better enough to offset the issues that new SSD drives often have.
Intel had to recall some SSDs a while back. I think they also had to fix other bugs via an urgent bios update. SandForce controller drivers, such as recent Corsairs, are affected by a BSOD bug that has been reduced but not fixed entirely. This new drive could have any number of issues, and you may be bearing the brunt of them as an early adopter. Granted, chances are very low. Intel always does their homework and testing, and its pretty likely that this drive wont have any issues. But I know if it was me, if I went for a new drive for a marginal performance gain and it was buggy as hell, I'd be pretty upset.
unless of course it was 512GB for the price of a 510 250GB. then I'd suck it up and wait for a new firmware.
EDIT number 2: I dont think the 710 replaces the 510 anyway, its a new enterprise drive. I'm not sure you would see much benefit. Wait for benchmarks and reviews.