Baseball analyst Dan Szymborski, every year, creates projections for MLB players by what he terms his ZiPS system. Here's a link to the post on FanGraphs which lists all the projections along with a bit of commentary.
I'm going to let you have at it rather than say anything really detailed here, except that the system doesn't appear to like batting average much at all. It's got Kris Bryant hitting 29 homers -- Rookie of the Year, right? -- except with a .226 BA. Javier Baez is projected with 30 dingers, but to hit .215 (actually, that would be a huge improvement).
Anthony Rizzo, another 30-homer guy for the Cubs, says ZiPS -- except he'll hit .235, regressing to his 2013 level instead of building on 2014.
And Jorge Soler is projected by the system to have just 345 at-bats and hit .229 with 12 homers. That's worse, in some ways, than the Mike Olt projection: 423 AB, 16 HR, .184 (even that BA would also be an improvement).
All right, now you're probably all riled up. Have at it.
UPDATE: As pointed out in the comments, I divided hits by PA instead of looking at the actual numbers in the second chart. The numbers given there seem much more reasonable, if a bit low, and I'm still mystified about Soler's playing time. All right, now you have something better to go on.