At the share values, here are the market values of a few companies for reference's sake. Please note that these numbers in NO WAY represent the number of cash (or debt) these companies have, and thus are not sufficient information to imply whether they might be in a good enough position to initiate a takeover.
MSFT: $271B (Unlikely because NVDA also has great lawyers too, although this would put the industry in a very interesting position)
INTL: $168B (Seems plausible to me. They have a lot of extra cash and might begin to fear other vendors' integrated solutions. Furthermore, their core business is being criticized by the hardcore media, and possibly leading in a market that evolves faster would )
AMD: $7.5B (Their market value might be higher, but I doubt they have enough cash for such an ambitious operation; furthermore, they are currently in an aggressive anti-Intel position, criticizing them for monopoly and unfair practices among other things, so I'm not sure they would exactlyput them in a better position for this...)
NVDA: $4.7B (Jen Hsun might be insane enough to invest in the competition and do a long-term takeover plan, but NVDA only has a fourth or perhaps third of the cash required for this operation; but this would certainly explain the G70 being released on the same day as ATI's conference call... Let's not get into ridiculous conspiracy theories though)
ATYT: $3.2B
I wouldn't really take "XBox is going to do well so MSFT is just investing a bit in them" seriously, it's way too much of a long-term investment for that. On the other hand, remember that some of these companies have investment divisions that are basically there to make some free money out of their cash. So if they suspect something, they might as well get some free money out of their better understanding of the market.
There are other companies I have not considered here; TSMC for example, because they might be possible but really aren't very likely at all.
Honestly I can't see happening, but who knows.
Uttar