If I thought that's what Sankey is then I wouldn't have traded for him.
		
		
	 
 If Sankey delivers this year even as a RB2, then flip value is pretty high next year no matter what anyone thinks of his talent level. I'm not high on him, but give him starter's receptions and TDs and it's hard not to take a chance on him.. From your other message, it seemed you were only shopping for young cornerstone RB and this was the only one you didn't get priced out of. It's not a strategy I would follow but 
its misguided to think he's at any risk to evaporate value. Even if they draft a compliment next year, which I highly suspect, there'll still be supporters who want him.
		
 
		
	 
Huh? Not commenting on the trade or on Sankey himself at all here, but ANY rookie is at risk to see a decline in value. If Sankey (or insert any rookie here) just sucks and can't beat out Greene (or _____________ mediocre veteran) his value will absolutely be down pretty significantly next year. And IMO it looks fairly likely that there will be a few RBs in next year's class that will be threats to be more than a complement to anyone outside of the elite guys (although it's way too early to say that definitively). Pretty much no player carries zero risk of a value decrease year over year.
		
 
		
	 
Bernard averaged 4.1 YPC last year and only had 170 carries but has an ADP higher than the best rookie WR last year (Allen). Barring a major injury he'll be rated a top 10 RB next year if he does even close to what Bernard did (which I think he will). I don't see Greene as any more of a threat to Sankey than BJGE was to Bernard. By the way, there's just as much risk with Evans as Sankey as they are both rookies so I think the risk a wash.
		
 
		
	 
You conveniently left out Gio's 56 receptions, 9.2 yards per reception, and 13th place fantasy finish in PPR leagues despite being on the short end of a timeshare. Gio's value didn't rise by default, like you seem to imply. Gio's value rose because he was a borderline fantasy RB1 and he looked like a straight baller.
Now, if Sankey puts up a 13th-place finish and drops a few jaws along the way, then sure, his ADP will rise. That's far from a foregone conclusion, though. Last year's RB corps was an aberration- over the previous 5 seasons, here were the RBs drafted in the second round: Isaiah Pead, LaMichael James, Ryan Williams, Shane Vereen, Mikel Leshoure, Daniel Thomas, Toby Gerhart, Ben Tate, Montario Hardesty, Lesean McCoy, Matt Forte, Ray Rice. How many of those saw their value go up between year N and year N+1? Forte for sure. McCoy's bumped up a little bit. Everyone else saw their value drop to one degree or another, either because someone else outplayed them for the job (Pead, James, Vereen, Gerhart, Tate, Rice), or because they got hurt (Williams, Leshoure, Tate, Hardesty), or because year N+1 saw the team invest in another RB (James, Pead, Leshoure, Thomas), and often some combination.
Evans could certainly see his value decline, but I do agree with Coeur that it's a much smaller risk with top-10 receivers than it is with late 2nd-round RBs.