El Dude said:
It may also depend upon how Rafa and Novak are doing, in terms of whether he plays RG or not. If one or both are killing it during clay season, he may gracefully bow out. Not because he lacks the confidence to beat them on clay, but because he realizes it would take monumental effort and focus, and is a longshot - and he wouldn't want to imperil Wimbledon.
On the other hand, if one or both are still struggling and he bows out before the tournament begins, and then they are both upset earlyish, he's going to be kicking himself as he sees a Wawrinka-Thiem final.
You are assuming that the only goal of Fed in playing RG is to win it. But, given that he is in the running for YE #1, RG gives a lot of points towards that even if he does not win it. Assuming Roger's #4 ranking holds at RG, then he can reach QF without even facing a top 12 player. Reaching QF at a Grandslam fetches you 360 points which is actually greater than what you get for outright winning an ATP 250 event.
So, my guess is that independent of what actually happens in the clay season before RG, Roger would play RG. However, he will take it easy in the early rounds (i.e., will not go all out to win his matches). However, if and when he reaches QF, he will start putting effort to actually win the matches, especially if one or both of Rafa/Novak have already been shown the door.