Initially I figured Zendaya would play Felicia or Liz- not because I had any sort of issue with the idea of her playing Mary Jane, but because I've been more of the mind that MJ is probably going to be more prominent than folks seem to be expecting her to be.
After all, the two big comic influences named for Spider-Man: Homecoming were Ultimate Spider-Man and Spider-Man Loves Mary Jane. Both of which feature MJ prominently and as a pretty immediate participant in Peter's life. It'd just seem odd to me for the director to refer to those specific comics if he planned on going the 616 route of introducing MJ to the MCU.
However, thinking more on it, I can definitely see Zendaya as MJ. She seems to have a certain charisma about her that was lacking in Dunst's MJ and probably wasn't there for Woodley's almost-MJ in TASM2. If Marvel wants to open up the role to other ethnicities, I'm game so long as they nail the spirit of the character.
Moreover, going back to my original point on SMH being influenced by USM and SMLMJ, I could see Marvel potentially finding a way to have their cake and eat it too by having Peter interact with MJ before officially meeting her in the classic 616 introduction as Spidey. Not that they would interact much together, but have it so that Peter keeps running into her through out the film as Spidey (without ever knowing her name) and keeps having Aunt May talk to him about going with "Miss Wonderful Personality" to the Homecoming dance.
Then at the end of the film, Peter rushes back to the house to get ready for the Homecoming dance and gets set up by Aunt May to go with MWP and discovers at the very end it's been MJ all along.
That'd be a good way of balancing out those influences, I think, no?