They won't continue the Spartan-II program, it doesn't make sense. Sure they were the most successful iteration of the program but that's why they've been creating Spartan-III's and IV's, to improve on that success. Now of course the II's were the strongest variation, but the UNSC would have to wait at least 8 years until they become as useful as the original II's because they'd have to kidnap 6 year olds and wait until they're 14 to augment them. This is why the IV program consists of adult volunteers, so they can go into the field sooner, and it seems as if the IV's are more effective and stronger than the III's, but we can't draw that conclusion until we see III's and IV's fight together, and thatcan happen because there are 5 surviving Spartan III's as of 2553.