The only thing that will for sure fall is his avg.
When his average comes down from .360+ to the .250-.260 range, his R and RBI rate will come down with it. Right now he's on pace for 98 runs and 143 RBI. If he has a very good year for him and finishes 85-35-110-.275 that means he'll hit 72-28-91-.260 the rest of the his 434 or so at bats.
Also for those talking 40-45 HRs, he hit 37 HRs six years ago and except for that season has been a high-20s to low-30s HR hitter. He's 31 so it's not like he's a young guy still growing into his body. His quick start will probably give him a better than usual year, but I think 35-ish is a lot more reasonable for this season. Talking about him as a solid, consistent 40 HR per year guy means you haven't looked at his career numbers.