Looking at the history of the series the most likely possibility is that it will be a game in between 4 and 2 that does not include or even mention Nero and involves Dante killing an old guy who wants to be god and meeting a attractive woman who tries to kill him at first but ends up becoming his friend and a possible love interest by the end of the game. If Lady and Trish appear they will have even less personality and even larger breasts than in DMC4. There is a 50% chance Vergil will appear and a 20% chance there will be a coherent explanation for it. The story will be interesting but badly written and the gameplay will be the best Devil May Cry has ever had but half the fanbase will still find something to complain about.
What I want to happen is a story that takes place after Devil May Cry 2 that explains Nero, gets Dante out of hell, gives Trish and Lady their original builds and personalities, includes Lucia and Nero as playable charicters with mutiple weapons that have different
movesets and brings Vergil back with a coherent explanation. ( an enemy that isn't an old guy who wants to become god would also be a good idea, but they can repeat the woman who wants to kill Dante but then becomes a love interest plot point, they haven't messed that up yet)