That is absolutely not the case. Obama promised her nothing - remember, she really, *really* didn't want the SoS job when offered it. It took a lot of persuasion from her and Bill to get her to accept it.
And in terms of a seat at the table, that's my point. Going to the convention with a list of demands and prolonging the healing process guarantees you fuck all. If you want to be at the table you need to join the table, you can't stand on the outside shouting insults and attacking the nominee. And Bernie won't be Hillaries VP because that would be a shockingly bad political move that would significantly hurt the ticket in a number of ways.
The way Bernie makes a role for himself in the party going forward is by actively supporting the party. If he wants to play the independent card and demand a list of concessions then he'll get nothing and go back to being impotent and on the fringe. If he does what Clinton did in 2008 and actively back her and the party, without demands, then it's a different story - he *should* have a role in the party, but whether he does or not is down to him.