This is sort of like saying the world wide web is a fad. Many people made that argument, but a lot of desktop apps got replaced by websites even though they were supposedly inferior.

ChatGPT works fine as a website and you don’t need to buy a new computer to run it. You can access your chat history from any device. For many purposes, the only real downside is the subscription fee.

If LLM’s become cheaper to run, websites will be cheaper to run, and there will be lower-cost competition. Maybe even cheap enough to give away for free and make money from advertising?