The article in Science concludes with this:

"Weindruch and his collaborators plan to continue monitoring the remaining monkeys, which could stretch the study's length past 3 decades. "If we reach the 40-year-old life span, the study could continue for another 15 years," Weindruch said."

The NY Times article says:

“Ultimately the results seem pretty inconclusive at this point,” Dr. Austad said. “I don’t know why they didn’t wait longer to publish.”

So, I think it is too early to draw any conclusions about longevity. Though, it does seem prudent to note the reduced rate of diabetes, cancer, and heart/brain disease in monkeys with reduced caloric intake.