Gun bans, panick buying, availability and pop culture have a lot to do with the price of firearms. With a $300 rebate you can't go wrong with a SIG 556 for I would bet they will never drop below $900 so the most you would "lose" ever IMHO is $100. With the release of the 516, I would buy another 556 or more now with the rebate while they are cheap because once the 516 flops on an oversaturated AR market (every day new mom and pop shops start up making them), the 556 will become more popular and more accessories and parts will be available. Since the ACR is a bust before it's even out (thanks for the double promised price and lawsuits Bushy) and the SCAR is now three times the price of a 556, I don't see a better deal out there.
...the Sig 516 is just another AR piston conversion with all the inherent deficiencies...and the market is flooded with them...just about everyone is starting to pump them out...the Sig 516 isn't any different...mabey worse !...the 556 is a far superior rifle to any of the AR piston conversions...