Since, Natasha is on Tony’s side, (sources claim, but be careful what you read) DON’T FORGET, that Natasha is a SPY. She always remained loyal to Steve in “Winter Soldier” and the near ending of “Ultron”. She’s not going anywhere. Steve trusts her and know after what aftermath Ultron caused, he doesn’t trust Tony and wants to see what he’s up to (Tony may call himself a “genius”, but his actions cause everyone to be put in harm’s way). 

Team Cap!