Microsoft is in this business for only one reason, and that's to prevent other companies from eroding it's OS monopoly. They see a threat, that consoles are getting more powerful, and thus one day, can be your personal computer also. Most people on this forum, don't think the PS3 is a threat in that area, as they will always claim it's a game console, and will have limited appeal as a computer. That maybe so, but with each succeeding generation, a game console will be a little bit redefined, and Microsoft has help bring that about, by including a HD with each console sold.
Now MS will not release a keyboard, mouse, and browser for the 360, because they live in mortal fear, that a person will then not buy an OS for a PC. Sony has no worries in that regard, and so are in a position to offer consumers more choices.
Microsoft believes they can dominate this business in time, given they have the reserves to buy marketshare. Only problem with that plan, is that if Sony continues to make a profit, they will continue to be in this business. If Sony makes a mistake, MS will be there to capitalize on it, but Sony has done everything right so far. The company is making enormous profits off of the PS2, that will pay for the factories to manufacturer the PS3.
Sony engineers are very good at reducing die sizes, so the initial cost of the PS3 chipset is a very poor reflection on what it will cost to produce in three to five years time, and that is the important time when Sony makes it's massive profits off of the hardware. There is no question that Sony makes massive profits off of the PS2, as the cost estimate at this time for the PS2 is around $50 US.
Sony is a position going from strength to strength. The PS2 sales are not low at all, as matter of fact last December Sony outsold the original Xbox by almost 4:1, when Sony usually out sells it 2:1 or 3:1 each month. Microsoft main advantage this generation was in being the more powerful of the two consoles, and thus attracted a certain segment of the market. The perception with the PS3 is that it not the weaker of the next generation consoles, but the strongest, with the perception surrounding CELL helping that. Microsoft failure in Japan will be very telling on Japanese software houses, and thus Sony is in a position to repeat it's market dominance. I don't see anything to change that. Of course Blu-ray will just strengthen's Sony position even more, and that's why Microsoft is throwing it's full weight in trying to stop it. They know Blu-ray is important to this fight, or they would not have been so vocal in their HD-DVD support.
All these arguments now being said about Sony will be said again in 5 years time. Nothing will change, and people will still believe that Sony will fail simply because MS has practically unlimited money to lose. Microsoft frustration will be completely born by the fact, that as long as Sony continues to do everything right, they will continue to dominate this business.