Barcelona is expected to pursue the signing of a new striker in the next 1-2 years. Robert Lewandowski is coming to the end of his playing career, and soon, a successor will be needed. Right now, there is no obvious candidate from within, which is why someone will almost certainly be brought in.
Viktor Gyokeres has been heavily linked with Barcelona in recent weeks, and the belief is that he is the club's primary target. However, it is not the only option considered, and according to reports in England (via ED), the Swedish international Alexander Isak is only on the list of Can Barca.
There is growing speculation that Isak will seek a move away from Newcastle United next summer, and Barcelona he might try to take advantage of the situation. However, they could only make a move if they have the necessary funds, which will only happen if they return to the 1:1 rule of the League.