I'm hoping to run a certain RPG event this year, but it's so different from a usual convention adventure in some ways that I wanted to use the forums to gauge interest in it before I go ahead with plans to run it at Gen Con 2021.

Here's the major details of this event:

System: Kindred of the East (Vampire: the Masquerade), with the PCs being dhampyrs (half-vampires)

-This would be a two-part adventure; the first part would take place during the Boshin War (1868; the war that ended the samurai era), the second part in the present day.
-Each session would be 4 or 5 hours, with an extra hour added to Part 2's time for leveling up characters (basically the players deciding, in brief, what their PCs did in the intervening 150 years and using XP for Attribute/Skill/Discipline build-ups they feel are appropriate for that). Yes, that does mean there would be a time commitment of between 9 and 11 hours over the course of the convention.
-It's tough to say much about Part 2 without spoilers, but the idea is for the conclusion of Part 2 to be The Big Payoff, a really exciting conclusion.

Knowing all of the above, is anyone reading this both interested in participating in this event AND planning to attend the convention in person?

That's a significant time commitment at a con like GC.  It's doable for something like Vampire, which has a built in player following, but the story has to be really strong or you'll get people to show up for part 1 and then bail for part 2.  Also, you can't make the first part just all set-up for Part 2, which is another common mistake.

Most Vampire events I've seen solve this by having it as a continuous event/LARP, with the story developing across one extended slot (say 6 hours), potentially with a follow on next year, etc.  Also, stay away from Saturdays as that's when you'll have the most competition in a normal (?) year.  Another solution is to have 2 parallel tables running, so if you get reduced turnout for round 2, you can combine.  Good luck.