It's probably going to end up similar to the equally hyped objectiveC where the core language was made portable but few of the tooling/API's used for real world OSX applications ended up supporting anything but OSX in any production ready capacity despite GNUSTEP actually shipping a ObjetiveC/OpenSTEP clone for Linux.

For the time being swift on Linux is a case of a few PaaS vendors trying to product differentiate by also offering swift frameworks because they can(due to modern container wrangling) more then due to any real market demand.