Not even close. Sandy bridge has lasted so long mostly because of it's groundbreaking performance and OC headroom. Two things the current ryzen chips don't have.
It's been obvious for months that Zen would underperform. AMD has an odd habit of only starting the hype machine when they know they won't put out something good.
It's the smart decision to make considering how terrible zen will be performance wise - we've known since the AotS leak that Zen will only be on par with sandy bridge at best.
There is a huge issue with not using the same suite of games (and not even with the same settings in the games they kept...) in both reviews and then trying to draw conclusions about performance decrease/increase over time. It's comparing apples to oranges.
The 480 has terrible yields, and the functional ones AMD does get seem to all be wildly variant from the process' specs. Some cards undervolt really well, some are unstable out of the box, and they're all limited to around 1350mhz core clock speed no matter how good the PCB or cooler seems to...
AMD started the entire gimping trend with TressFX in 2013's Tomb Raider as well. AMD loves to play dirty when it suits them, but will call foul as soon as someone gives them a taste of their own medicine.
Refuting your AMD marketing FUD = 'lacking any real knowledge'? LOL.
Not even close to a fanboy, I've actually owned more AMD GPUs than NVIDIA GPUs in the last ~15 years. I usually buy whats best based on value. In fact, my current system even has an AMD GPU. But that doesn't mean I won't call...
A 970 clocked to 1500-1550mhz boost is on the same level as a stock 980 or 390x. What exactly makes you think it's going to fall off outside of the usual AMD FUD?