The most recent printing of Tropical beach is BWP50. They would have to rotate all 50 BW Promos for Tropical Beach to be illegal. This would include DRX Prerelease promo Altaria, which was just was part of a set just released at the beginning of this format. I find that highly unlikely. Pure speculation, yes, but I'd bet money Tropical Beach is safe for another year.
Plus, they could reprint Tropical Beach yet again at this Worlds, which would extend its lifetime even more (unlikely, but possible).