It's not like excellence had never been predicted for Cabrera. He's only 23, so you shouldn't assume that he won't improve significantly. He's pretty good right now, in fact: 16 R, 6 HR, 17 RBI, 3 SB, .291/.359/.505.
Is Cabrera going to maintain the 30/15 pace?
Well, so far he's hitting a few more fly balls than he has in the past, and his HR/FB rate (17.6) is much higher than it was during the previous two seasons (5.3 and 5.8). It may not be impossibly high, but it's still a big number. Yet if Cabrera gets another 440-460 at bats, then 13 or 14 more home runs is entirely reasonable. We know the speed is legit. He's stolen 28 bases in 317 career Major League games, and he had another 39 in 357 games in the minors.
Given Cabrera's age, his run and RBI-friendly surroundings, his entirely sustainable BABIP (.289), and encouraging comments like this...
"He's just really grown, physically and mentally," Yankees hitting coach Kevin Long said. "He gets good pitches to work. He's got a short, compact, explosive swing. You very rarely see him waving at the ball. We're seeing big dividends."
...you'd have to conclude that Cabrera can finish among the top-30 fantasy outfielders, with a line like 85-20-90-15-.290. That would make him a player worth owning in all leagues.