Barcelona didn't really need to renew Dembele's contract even if he had nowhere else to go. Also, if De Jong changes the terms of his deal with Barca to stay he'll just be doing what Umtiti and Pique and others have already done. Its not unprecedented within the dressing room.
Depends on what's important to you and how else you make it up doesn't it? Its not like his wage from Barcelona is his sole source of income.
Its known that De Jong has loved Barcelona his whole life, his family used to holiday there, his girlfriend loves the city as does he. If you want to be in a place, and you live pretty comfortably, then what's the difference?
Everything De Jong is 'losing' he's losing on paper. He hasn't been paid the original value of his deal at any point. So, in reality, while he wouldn't be getting what he originally thought. The wage he's been living on won't change drastically.
I think people want to believe this will happen and so are finding reasons why it might. I would like to believe it will happen. De Jong would instantly take our midfield up a few levels. It would actually be shocking to see how much he would improve us. We've gotten so used to the standard of midfield play we've had for the past few years, we've forgotten what is like to have someone who can really pull the strings from dep.
I just see the other side of the coin. De Jong loves Barcelona, he's literally living his dream, his actual take home pay won't change all that much if he agrees to what is, in reality, a nominal pay cut. Lots of other Barca players have done it, so he won't be the only one. If Barcelona are serious about giving him that option I can see him taking it.