I think it will be Crabtree and Williams. (I would have said Ginn but he is injured.)
I think the 49ers are "playing possum" with Moss. They know opposing defenses will be on alert to Moss and Manningham since they didn't get any real film on them in the preseason. I suspect they want the opposing defense to get into the game before they bring in Moss. And I would expect Moss to be a decoy and run some shallow routes to lull the defense at first.
I'd love to see Moss and Manningham come in the first play and start gouging the defense. But that just doesn't seem to be Harbaugh's personality. My fear is that playing it close to the vest against the Packers offense could put us in a hole early.

Dude you are wrong...so wrong. So far I haven't found anyone making a good point about Ginn not having a place in the offense as a receiver. I will make a case for him to be one --speed. Once his wheels are better he can clear out for others ..ahemm ...crabtree.... to have space behind/underneath. Contrary to popular opinions, he does know how to catch the ball thrown his way. No denying that he have had some boneheaded drops but he also had some good catches too and some of those for 3rd down conversions. Even in the latest 4 preseason games, there was a 3rd down catch that I remember. And the one that Smith forced to Moss, Ginn was open ...wide open...on a crossing. We need Ginn to stretch the defense. We missed what he provide last year against the Giants in the NFCCG.
Jenkins won't see time over Moss or Manningham. Plus Ginn will be used throughout the year at WR as well