I think the flash forward should've only shown Walt with grown out hair, a fake ID and buying something on his birthday. The M60 and the ricin ruined a lot of the suspense. We would've had 30 minutes to figure out what he was going to do with them instead of 8 weeks.
Still an awesome finale but the flashforward took away a lot of the suspense. We would be blown away if he pulled all this off and we had no idea the M60 or ricin were coming.
Personally, I think it was just Vince and the writers flexing. Were going to show you what happens in the end and you'll still love it. Touché