The advantage of having lighter wheels is psychological, and it's a two-edged sword.
On the one hand, you'll likely climb faster just because you think you can climb faster, or you're supposed to be going faster up the climbs because you've got these super wheels.
On the other hand, if you happen to NOT make the time cut with this expensive technology, you will probably feel even worse than if you had done it on heavier/fatter wheels/tires.
Use your existing equipment. If you miss the cut by 5 or 10 minutes, then you can blame it on the equipment, and swear to come back next year with the lighter wheels. At least you'll have a positive story to tell.
IMHO, equipment is insignificant. Nobody needs the carbon fiber Di2-equipped racing bike with the carbon wheels unless they're racing a Grand Tour. For anyone else, it's all for show, and it just makes the guys n the steel bikes with the fat tires feel better about themselves when they drop you on the climbs. Besides, you could have the fanciest bike/wheels on the ride, and most people either won't care or won't know what it is, so "for show" isn't even a valid reason!
Luis