Selling Rakitic most probably had been decided when they bought De Jong.
If Rakitic undertakes being a substitute, then fine, they can keep him like that, but probably he wants to play.
Coutinho's possible sale is a mere financial matter, they will get rid of him but only for considerable amount of money.
If Valverde stays (I sincerely hope he will not) there is no use for him to play further. But in case another coach comes, there is perhaps a slight chance that he can reincarnate himself, preferably in a different position.
What I don't understand is Umtiti - if the gossips are true.
He is a great player and at his best he is much better than Lenglet.
I doubt that a sane manager would get rid of Umtiti, simply because he was injured for a long time.
First of all the only Catalan player there is Piquet. The rest are either Spanish or "adopted" Catalans.
Secondly the high-management knows that by relying mostly on "domestic players" - as you put it - would be a popular trend, but would not lead to either results or to form a newer style - based upon them.
You are absolutely right, the present La Masia adduction is not very good, neither Alena or Puig are good enough for a newer Barca setup.
In my subjective opinion Alena will never become a great player, (sorry to say but whenever he plays I only see a slightly better version of Andre Gomes in him, their physical characteristics, moves are pretty similar).
Puig has more talent, but at present he is perhaps good for the bench only, the others are more or less forgettable as first team material.
But the La Masia thing - that is repeated like a mantra over and over again - is a natural one, there are peaks and bottoms, only idiots could think that it is a "factory" capable of producing better and better players - continuously - all the time.
It did produce great ones for say 10 years, so it is inevitable that a slight drought comes for quite a few years to come... One can do nothing about that, because it's the most natural tendency...