None of us really know who will be coming or going but this is what I'd like in terms of incoming transfers.
Eric Dier - I'm surprised more people don't talk about him. He's a boyhood Utd fan, he was brilliant last year playing as the holding midfielder for Spurs and he can also do a more than decent job at the back. He could even be a stand by at RB in case Valencia gets injured. Also I don't think he's unattainable like Kane or Dele Alli might be. He's well acquainted with the PL so no settling in period will be necessary. Him and Pogba would be a good partnership I think.
Douglas Costa - He's recently made noises about wanting to leave Bayern and if he does move we really should go for him. He is exactly what we need. A quick, talented winger who can play on the right. He can cross, shoot, dribble and doesn't shirk from his defensive duties as well.
Antoine Griezmann - The rumors about him seemed to have cooled down a bit lately but if we can get him to play as the SS, we immediately add a 15-20 goals per season player who does more than just score.
As for who should leave, well at present the senior players in our squad are Rooney, Zlatan, Carrick, Valencia, Young and Schweinsteiger. Barring Valencia a case could be made for all of them leaving this summer but that would be disastrous IMO.
We need leadership and experience these players provide and of the 6 atleast 3 should remain here. Valencia is a certainty to stay and I don't know about Schweinsteiger's situation but out of Rooney, Zlatan, Carrick and Young atleast 2 must stay. I suppose Young will probably go but I hope Carrick can be persuaded to stay another year.
If Zlatan leaves I don't think it would be the worst thing as it would allow our team to be not be so dependent on a single individual for goals, kind of like when RVN left in 2006. If he leaves I wouldn't buy any striker but rather play Rashford at the spearhead of a front 4 of him, Martial, Griezmann and Costa (provided the latter 2 come, if not Mkhi in the center with whichever winger we buy). This system provides fluid movement across the front line capable of quick interchange and all the players present a goal threat. We would be a more well rounded team than we are at present.
If Zlatan leaves I would keep Rooney for his experience in the dressing room. But if Zlatan stays then I would let Rooney go.