I categorically reject the notion that these bugs are intentional. If you have ever worked in the industry and designed systems like this, you would know that intentionally planting bugs in firmware to boost profits while the CEO cackles in his evil underground lair is purely fantasy. Companies can get into huge trouble for pulling shenanigans like this.
However, I will take the middle road, and say that Sony does know that these bugs exist, but they were not intentional. Sony, more likely than not, designed the latest firmware revisions specifically for the PS3 slim. They may be putting off implementing a fix so that they can milk some cash out of people going to the store to buy new PS3 slims so that they can remedy a broken fat PS3 and get back to playing games. Putting off a firmware patch can be done by feigning ignorance of the issue (like what sony seems to be doing right now), and once the issue reaches a boiling point, they will probably extend the release deadline even further by putting some read tape in (such as "it's a really complicated fix, and it's going to take time") In a way it is a fortuitous bug for Sony, because they might be able to milk some more money from customers.
However, the issue at hand here is that older versions of PS3 have over heating issues due to the Blu-Ray player. I think it is now common knowledge that blu-ray player speed and encryption rate have been boosted to allow 3d movies and games which will require more processing power. Of course, the PS3 slim uses far less power than any of the fat PS3s (only about half as much, and 1/3 as much for 1st gen. models) so boosting blu-ray performance is not an issue. The other PS3s are overheating. Those that have the 1st generation models have had the most severe failures, as in 60GB versions not being able to read any discs, and YLOD.
This is probably catastrophic failure, and a burned out circuit. Newer models (gen 2 and 3) use less power than 1st gen, and have issues with Blu-rays and ps3 games, but not DVDs. Processing Blu-ray and PS3 game data is processor intensive, and thus generates a lot of heat. Decoding DVDs does not use nearly as processor intensive, so they work fine. In addition, often times, if the unit is left idle for a while, and gets a chance to cool down, games can be played for a period of time before overheating returns. I am convinced that their is a bus between the blu-ray player and the CPU that is overheating, or getting damaged here.
Which leads to the last issue at hand and reflects very poorly on Sonys management. The original PS3 and the PS3 slim are very different systems, when it comes to fabrication process. your talking 90nm process on some, 65nm process on others, and 45 nm process on the newer versions. Not to mention other minor hardware tweaks made in each successive generations. Any competent embedded system designer or engineer will tell you that you cannot use the same firmware for three completely different systems just because they share the same architecture.
The new paradigm for designing these types of systems is no longer processor speed, or compexity, but POWER CONSUMPTION. Sony has failed terribly in seeing this trend, and I think that we are just seeing the tip of the ice berg right now. Heat issues are progressive, they build up over a period of time (when the system is in use) and some useres use their PS3 more than others. This means, more likely than not, all original PS3 systems will fail. And what makes it really bad is that these systems would have been fine if it were not for mandatory firmware upgrades that essentially cripple any non-PS3 slim over time.
I can't see the future, but I will say that if this is the case, it may just lead to people completely losing faith in sony, and lead them to becoming an irrelevant brand, just like Sega, Atari, and all of the other long forgotten systems.