No, I think Messi can still return to Barcelona to play for his childhood club before retiring there as the club legend.
Well as far as i know, Messi did not really had to leave Barcelona at all. It was just the case, that Barcelona could not afford to pay Messi his extremely high salary. They have paid him around 550 M€ for a 5 year contract, that are 110 M€ per year, which is probably 5 times more than other world class players are earning. That was the reason why Barcelona has such extremely high debts now and is still in danger of going bankrupt.
Messi could have stayed back then but of course for a salary that would have only been a fraction of the old one. So it was not like he was forced to leave or something. He just wanted to continue to earn ridiculously high amounts of money and he could do that PSG.
I have already said it, the major concern of players is to continue to earn highly ridiculous amount of money. I first asked this question that if Messi loved Barcelona that much, why not take some pay cut.
The same thing happened to Ronaldo. When the bid from Saudi came, I told people that Ronaldo will go for the money but they said that Ronaldo will like to play only in Europe and possibly in the Champions league. But today we have seen where Ronaldo is.