You know, there is something that I'm as curious about as the last character...the last Mii wave. If they end up showing the Miis before the fighter that will probably be one of the most tense moments we've had in Ultimate's lifespan because due to the last character being revealed soon, the stakes are raised even higher. Not to mention I'm expecting it to be a slaughter. Looking at the last Mii wave, I feel like they will do another round of fan favorites. Examples being Crash, Doomguy, Hayabusa, Phoenix Wright, Professor Layton, Neku, etc. Assuming that none of these are the last fighter, I can easily see any of these being Mii'd pretty soon.
It would be heartbreaking but at least it would be something, a pleasant surprise before the final character which will probably be disappointing to many people.