I think Microsoft has seen they have been able to get by with whatever flaws the 360 has for this long and so are hoping to get by a little longer until they get their 65nm hardware redesign out. At that point any old systems coming in could be replaced by 65nm hardware. If they do that, then they won't have to face replacing the entire 360 hardware base as with a recall, they would still just be replacing only actual failed consoles as they are doing now and thus would still never have to admit there was ever any significant problem and therefore avoid the negative press admitting to a wide problem could generate.
They just need to be able to contain this until they get to that point. Once they got to that point, with people receiving 65nm versions when their console breaks (this is assuming no new problems with the redesign), then a lot of this will be forgotten. One thing Microsoft has on their side is that this is an industry where a large base of the customers are wanting them to do well in order to be able to play the games they have already invested in and also continue to have good games developed for in the future. Because of that, Microsoft can get away with more with their userbase than other companies can in other industries, but they can only push that so far. They must have some sort of a plan to address this that they will be implementing in the next few months. There is no way they are just going to continue with things as they are - I am thinking they are pouring everything into their 65nm redesign and that will be the answer to a lot of the problems.