Personally I think it's possible that we end up with "13" members: Luffy + 11 crew members + the ship.
While I wouldn't take stock in a lot of theories I don't agree with commonly repeated reasoning like "11 total because Oda likes soccer" which I hear way too often by the community as a whole
For me, I'd invest time looking at wordplay which Oda utilizes a ton:
The crew is called "Mugiwara no Ichimi" which could double meaning from not just the "Strawhat Gang" but also "Strawhat of 1,3". If you look at both sides of the Sunny, the default numbers for the soldier dock doors are 1 and 3.
We're missing the 2,9 devil fruit and if you add up the numbers of the crews devil fruits the sum is 325 or San-Ni-Go. "Sunny-Go" being the name of the ship. Oda doing this by accident is, mathematically speaking, extremely improbable.
I think the final numbers of the crew are also open to interpretation. Luffy and official members (currently Zoro thru Jinbe) all have their numbers. Does the ship count? If a kid joined as an apprentice, would they count? Zeus doesn't seem to count.
Overall I think it'll be Luffy + 11 fighting members (probably Carrot and another swordperson as the last 2) + the ship.