I'm mostly indifferent towards HW4. Anything new introduces risk and unknowns and we know what to expect with HW3. Also, any additional capability of HW4 is unlikely to be fully utilized for quite some time. There are hundreds of thousands, if not millions of 2016-2023 Tesla models on the road running HW3 including some that are still being sold today. During an earnings call earlier this year, Musk remarked that HW3 could be 2-3 times safer than a human while HW4 could be 5-6 times safer. Twice as safe as a human or even
as safe is still very impressive to me and HW3's capabilities haven't been fully utilized yet. I'd take HW4 over HW3 if it was an easy choice, but I wouldn't worry about getting HW3. I knew HW4 was around the corner when I took delivery of my vehicle, but didn't let it give me pause because I know that even HW3 will continue to improve through software for years to come.
My iPhone is four hardware versions behind, yet it continues to get new features, capability, speed, and stability over time through software updates and is still far faster and more capable than it needs to be. I've tried to justify upgrading to an new iPhone, but there's no perceivable difference between my old iPhone and a new iPhone for the things I use it for every day and the battery has only degraded 13% over the last half-decade.
There is one compelling reason I'd like HW4 and that's for the improved resolution and color of the new cameras, but even HW3's cameras are more than adequate to provide evidence in the event of a collision, for example.
And, let's be honest, even HW4 may never be capable of fully autonomous driving as safely
and smoothly as a human - that might not happen until HW5 or HW6 if it happens at all in our lifetimes.
The simple fact that Tesla isn't offering an upgrade from HW3 to HW4 the way they did from HW2/HW2.5 to HW3 suggests that they believe that HW4 simply isn't necessary for full self-driving to be safer than a human.