If indeed Lewandowski asks for a salary increase, it seems I agree with you that he will be sold to another club to make a profit rather than increasing his salary but it won't have a big impact on Barcelona.
I have previously heard that Lewandowski actually wanted to be sold by Barcelona but he refused when there was a big offer from a Saudi Arabian club so maybe Lewandowski received a bigger offer from a European club.
The question is quite difficult, which European club is willing to buy old players at high prices? It's a little impossible but it could happen unless he gives a very strong performance this season and releases him in the next transfer market to give confidence to other clubs to offer him a big salary even though he looks old.
But it quite difficult for Lewandowski to improve his performance because his old age prevents him from increasing his performance level because his physique is definitely very different.
Barcelona is financially off the radar at this point and Lewandowski asking for a pay rise will leave them with no other option than to offload him. Yes, he would have left earlier had he not turned down a huge offer from the SPL but what could be the cause? Him asking for a pay rise means there have been a green light from a club in Europe and yes it’s very possible because I feel he still has some sting in him and could help you get huge number of goals enough to make your team succeed.
So Barcelona would have to use him to his full potential then try to offload at the end of the season and make way for younger striker who still proves effective, cause with the way things are I don't think Lewandowski is still fit for the pressure in European football, despite the fact that he's experienced it's not enough to keep Barcelona going, they'll need a younger, stronger and talented young lad upfront to replace him sooner or later.
I think Lewa already used his full potential at Bayern and at Barcelona he is just a shadow of is former self and I'm not saying this in a bad spot , this is just the plain truth. This also doesn't mean Lewa is not a great striker anymore but we can see that is has a certain age , we can see he lost his touch , we can see he lost his reflexes and also he seems tired.
Regarding his transfer , I cannot see any team from europa that would want him so my guess would be MLS or Saudi Arabia for him.