There is indeed already open source models rivaling ChatGPT-3.5 but GPT-4 is an order of magnitude better.
The sentiment that GPT-4 is going to be surpassed by open source models soon is something I only notice on HN. Makes me suspect people here haven't really tried the actual GPT-4 but instead the various scammy services like Bing that claim they are using GPT-4 under the hood when they are clearly not.