AFAIK, Rulebusters are only available to the members of each particular program. In other words, as a member of Frequence Plus I can get a double miles award ("redeem from the opti-miles schedule") only on AF flights and only using F+ miles. Delta is the same. SkyChoice rewards (the ones that cost twice as much but aren't capacity controlled) are only available on Delta flights and only using SkyMiles. So, unfortunately, your redeeming potential for exact dates using double the amount of miles probably won't increase when NW joins SkyTeam. You'll still only be able to do that on NW. That said, as other posters have indicated, with more partners and more combinations, you should have a better chance at redeeming regular (capacity controlled) awards.