Not all that much changes when it comes to Beltran's expected production. He goes from one pitcher's park to another and will probably be backed by Pablo Sandoval in the lineup. It's not like Beltran was on a 30-homer pace anyway, his value lies more (real life wise) in his awesome plate discipline. For fantasy purposes, Beltran may see a slight drop in his RBI pace, given that it's no longer Jose Reyes getting on base in front of him.
Quick scouting report on Zack Wheeler
I've had a chance to see Zack Wheeler in person multiple times this summer, so I have a pretty solid opinion on him.
What I like about Wheeler is what can be described as above-average to well-above-average stuff, especially his curveball which looks unhittable at times. His fastballl has good movement and he is learning to work his changeup effectively off of the heat. He should post above average strikeout rates in the big leagues.
The bad news is that I really don't like his mechanics. There's nothing complicated about his motion, but his arm lags way behind in his delivery, causing him to have trouble locating his pitches consistently (4.8 BB/9 at high-A this season). The arm action also pushes his injury risk into the danger zone, as he is putting extra stress on his shoulder and elbow each time he throws because the arm needs to "catch up" with the rest of his body. There is no guarantee of an injury in the short or long-term, but the risk is certainly elevated.
The bottom line for keeper league GM's is that Wheeler is an exciting young arm, but one with multiple question marks (control/injury risk) that work to counteract some of his top-end stuff.