Guitars (and other instruments) will remain even with the prevalence of electronic means of creation, in the same way the paintbrush and pencil are in no danger from Photoshop. The typewriter was replaced by software because instruments and implements offer what a typewriter cannot.
Nuance.
The "art" of paintings, drawings, and music lives in the nuances and life of the art; the imperfections or subtle changes. Writing is an assembly of language characters to convey the art. The nuance is how those character elements are arranged and interpreted, and thus the means of doing so are unimportant. However, an errant bristle or subtle slide down a string give life and nuance to an art without explicitly standing out on its own.
No one is saying they are going away completely just that they are mostly replaced (just like many other instruments). The number of people who live from playing the guitar has dropped to almost nothing the last 30 years. Even really really great musicians are hardly being booked any more.
Nuance.
The "art" of paintings, drawings, and music lives in the nuances and life of the art; the imperfections or subtle changes. Writing is an assembly of language characters to convey the art. The nuance is how those character elements are arranged and interpreted, and thus the means of doing so are unimportant. However, an errant bristle or subtle slide down a string give life and nuance to an art without explicitly standing out on its own.