Look at it this way, if oracle loses, then what’s the implications of the software licenses in general. The whole point is that they were protected by copyright. If that’s shot down, then what’s at stake?
Not saying I side one way or the other, simply that I don’t think it’s clear. Depending how the court rules one way or the other could have a huge impact (as you pointed out).
An Oracle loss would not damage the legal framework that the software industry has been operating under. Oracle's loss would only confirm the non-existence of a new class of copyright that Oracle is trying to invent (one that appears to be patent protections with copyright duration, enforced in part by trademarks). An Oracle loss would not undermine the legal foundations of existing copyrights on code that implements an API.
No one has ever thought that you could stop people from copying APIs. If they did all sorts of things like Linux (hi Unix), Wine, Windows Subsystem For Linux, AMD x86 CPUs (ok, Intel might have licensed them to avoid anti trust issues), Intel x64 CPUs, and so on would not exist.