We'll see how Valverde will integrate Coutinho and Dembele into the team and how Suarez will play in the remainder of the season (though there is no way he'll leave even if he'll go back to his bad form) but right now I think bringing Griezmann into the mix could cause us more problems than good. Not because he wouldn't fit (in opposite, I think he would be a perfect fit) but I just don't see how all 5 big ones - Messi, Coutinho, Dembele, Suarez, Griezmann - could play together without risking defensive stability of the team (which is clearly important to EV and rightfully so) too much.
I would prefer to buy younger striker like Werner and possibly let him on loan with his team for another season to play regular and keep developing while keeping Paco as a backup for another season. Then bring that younger player in 2019 to slowly integrate and take over from Suarez.
Or we could get another versatile forward (alongside Arnaiz who I think will be promoted in summer) who could play in both wing positions and as a striker so he would get enough playing time even if he would be primarily a backup. Don't know who that could be though.
I agree. I think it would be a mistake to basically force Valverde's hand completely in the coming years by buying yet another attacking superstar who has to play all the time.