If both Grealish and Kane come, then Bernie will 100% be sold, we can't accomodate that many players.
If just Grealish comes in (and no striker), then Bernie may still be sold, but there is a chance to keep him, and it could work out.
Look at our pre-season and look how dominant our wingers are in terms of our goals, it's very similar to last season, we don't play in service to our striker, they play in service to the team. Mahrez and Edozie alone were involved in most of the goals over these last 3 games.
Now the argument is the striker was Ben Knight, anybody is an upgrade over him, but Kdb, Grealish, Sterling, Ferran, any of them makes that false 9 tick even better.
We are most likely a better team with Kane just considering his quality, but if he doesn't come in, and there is a chance to keep Bernie, we could still be dominant in the false 9 (especially with Gundogan having a free attacking position) as we saw last season.