That's a good question. All the guys are usually super pumped and motivated to get into great shape for the first film possibly due to the fact they know this will be their career making role. Bale, Evans, Hemsworth all huge in their first outing.
However come the 2nd film and them having a little more clout/security under their belt, i don't want to say they slack but maybe don't push themselves as hard as before. All of the mentioned were somewhat smaller in their 2nd screen outings (hell throw toby maguire in there as well).
Hemsworth talked about how it's brutal to get into thor shape and i believe it actually became a point of contract contention vs how much he was actually going to make for an avengers 2.
So as for cavill i suspect he'll still look great but probably less shirtless scenes for a reason.