I love AD, but yes... That's about as high as his ceiling is ever going to be in the NFL. Being a Niners fan of 30 years, I've seen just about every snap that he's taken thus far in his career. As much as I'd love to see him break out, he just hasn't been anything more than just impressive enough to stay on a roster.
I still like him as much as just about anyone in the league around the goal line, and I could see him getting 6-10 carries/game as a change of pace or 3rd down back, but I don't think he'll ever have the ability to snag a full time job like many are hoping. He actually had some fairly significant opportunities to impress during his first two years in San Fran, and he just never quite did enough.