Well, LLM's are probably here to stay. I'm not sure that OpenAI has found a viable business model, and as Matt Levine of Bloomberg put it recently, OpenAI is a "money furnace", that takes stupifying amounts of VC money (and, more importantly, cloud compute capacity) and burns it for purposes that do not remotely pay for the cost.
The biggest reason not to rely on ChatGPT specifically, is that it is likely to either disappear or else become much, much more expensive in the future. But, if you can use DeepSeek or some other much, much cheaper alternative just as well, I suppose that will do.