@spenmk Waiting is hard but I think the longer response time is a result of when your son applied and the holidays. Fewer students apply Sept - Nov so the turnaround time is faster. Since your son’s GPA and SAT scores meet the Kelley criteria he should be accepted. FWIW - Kelley converts 5.0 scaled GPAs to 4.0 GPAs but I really don’t think they recalcuate the A-, B+ to the 3.7 and 3.3…that would require a lot of effort. Yes, once enrolled - IU students’ GPAs are calculated that way but highly unlikely as part of admissions.
Per Kelley’s site, they state a 6 - 8 week window after IU acceptance for Kelley notification. Your son was admitted 12/30 so only 4 weeks have gone by. Unfortunately, you will have to wait it out. But, I really do think your son is in. 
From the Kelley website
3.Once you have been admitted to Indiana University, and you qualify for direct admission, you will receive notification of your direct admission within six to eight weeks. If it has been longer than eight weeks since your admission to IU and you have not received an email or letter about direct admission, you may email us.