Honestly, I feel like Crash is a rare example of a character who, I personally feel, could realistically be anyone of these fighters.
I could see Crash get revealed next because Crash 4 is coming to the Switch around the same time as we are expected to get the next reveal. However, and this is definitely the most likely scenario, Crash has probably the highest chance out of any candidate to be revealed as FP10 at E3 considering Nintendo usually saves the heavy-hitters for around that time, and June is the Crash month. But, and this may be an unpopular opinion, I also think their is a slight chance if Crash isn't 9 or 10 that he could be saved for the very last reveal. This is definitely the least likely scenario for me and I do think if FP9 or 10 isn't Crash, his chances may decrease quite considerably, but I do have a feeling that their is a chance Ultimate may end on a high note, and a much better note than most other Smash games. I understand that Smash usually doesn't have the best track records when it comes to final reveals, but with Ultimate being the ultimate Smash game, I do think its possible Sakurai may really knock this Pass out of the park and end Smash Ultimate with a bang. I do think this is the least likely scenario, but its certainly a scenario nonetheless and I'll always consider this a possibility.
Out of these scenarios, I think its more likely Crash will be revealed at E3 as FP10, but realistically, Crash is a rare example of a character that I honestly cannot rule out completely for being any one of these characters.