I'm also with "do the right level now, and cross future bridges later". You do need some forward planning, but don't let future possibilities scare you out getting the right placement now.
And if MIT doesn't worry about high school diplomas, then neither will I.
One thing, though, is I don't think it's good to have a "gap year" in maths. You need to keep your maths thinking cap on to stay sharp. For someone finishing Calc BC in grade 10, while Stats and Comp Sci are perfectly decent courses to takes the next 2 years, it's still better to continue with actual maths courses. If you can get access to courses in Multivar Calc, Diff Eq, or Lin Alg (local uni or a rare high school) that is a good option. Or maybe instead then would be a good time to take those AoPS (or whoever) courses in Counting & Probability or Number Theory that you hadn't got to yet.
