The concern I keep hearing about Barkley is whether he can make all of the throws a top NFL QB must make, particularly downfield. I believe it is generally accepted that the guy has the leadership qualities you want in a QB.
We will see how the rest of the year plays out. It is just as likely that he will have a great pro day and shoot back up the charts. The likelihood is that just like this year and last, teams are desperate for QB talents (well, except the Chiefs) and even if he does slip, it won't be past the first round even I some don't see him as a first round talent (see Tannehill). But he is obviously far from a sure thing that Luck and RGIII were...