I'm not sure it's possible to know whether everything has a scientific explanation.  There are plenty of things we haven't yet explained, but that doesn't mean we won't find a way sometime in the future.  I have no idea what the world might be like a century from now, let alone another thousand years or more.  We may find fantastic new ways to observe the universe and understand things we just can't see now.

I don't assume everything can have a scientific explanation.  A lot of philosophical questions may only be answerable through personal experience and meditation on the subject, or by the adoption of external beliefs.  Now matter what happens in the future, there will likely be unanswered questions for as long as there are beings capable of asking questions.