He's always been a HIT template player, who never quite translated it into MLB success enough to hold down 1B. The theory was always that, like guys like Votto, Edgar, and Mauer, he'd eventually learn how to pick on the pitches he could punish and start doing that.
It's ALWAYS suspicious when a player has a breakout (especially a PWR breakout) in his FA walk year, but I wouldn't worry too much about the late slide in the power department. He's not going to hit for as much power as he did in those first two months, nor is he going to hit for as little as he has the last month or two. He didn't fake those first HR's; he's obviously capable of hitting pitches out of the park regularly. The real questions are: was this PED-driven, or was it a legit plateau leap. I generally tend to think the latter, but I've been beaten down by life enough to admit the former is more probable than I'd like.