I somehow agree with your conclusions, mostly about keeping the conversation here on topic, but I think your comparison may sound a bit inappropriate due to a completely different base cost, as well as the features expectations for cereal and cars respectively
To be honest, one could call it a proverbial "apples vs. oranges" draw.
The decision of buying or not cereal simply doesn't imply any real financial consequences, so from a psychological standpoint is totally insignificant, which we can't say about a car purchase, at least for 99% of the population
We also can't blame anybody here for "poor decision making" if Tesla is not giving any heads-up information about upcoming changes to its lineup. In order to make any well-educated decision one would need to be able to assess all the factors, which clearly wasn't the case here. Let's be fair about this.
However, as I mentioned before we need to keep in mind that this is one of the most innovative companies ever in existence, so we have to be prepared that continuous improvements and constant change are a norm for Tesla and we should take it into consideration when making any purchase decisions. After all, that's why we all love Tesla, right?