We'll see when he's a senior. I can't speak to the Harmon comparisons because he was before my time. I think Tavian and Russell had better vision (though Wadley is quicker and faster than Russell). It's conceivable that Wadley could make that leap, since he's only two games into his junior year.
The Sanders comparisons are huge hyperbole, though. Sanders was quicker than any back Iowa's ever had, but more importantly he had better vision and balance than any player I've ever seen. That combination is why he's the best runner in football, ever, at any level.
Oh, and I love Daniels and think he's gonna have a very good year (1,000+ yards, 6-ish ypc), but I don't think he'll be drafted, given how devalued RBs are, in the draft these days. I mean, he'll get a shot in camp, probably even a UDFA contact if he stays healthy this year and does as well as I think (or better), but probably not drafted.