That has absolutely nothign to do with sales plummeting.
And in a handheld device the size and form factor of the device are a very important feature to the majority, HDMI in consoles is not, with an overall install base of probably less than 5-10%. So you're comparing apples and oranges.
Yeah well "plummeting" maybe not, because that's too subjective, but the sales dropped to two thirds of what they could IMO have been without the introduction of the respin.
If I discard the exaggerated pre-Christmas data and look at July, August, September (slow/normal months for CE sales), the DS phat sold 54k per week. Then comes the Christmas rush, then comes the last week of January where the DS lite was announced and a huge inventory blowout happened in the week (111k). The following four weeks are the time between the announcement and first availbility of the DS lite, and the sales fell through to 33k units per week. Even if I factor in the blowout week, it's down to 48k.
Starting with DS lite availability we're looking at 150k per week average even in the slower months of the year.
I still believe that jump is significant and has a lot to do with the introduction of the revised model.
Now, yeah, it's not exactly the same
kind of revision with the 360, but there is common ground. Both revisions make the product
better and more desirable. Making a home console easier to hold in your hands isn't necessary. Giving a portable gaming device with specialized integrated screens more video output options isn't necessary. It's no surprise that both revisions only improve areas that are relevant to the intended useage of the respective device.
OTOH when Mr Microsoft representative says they don't have plans for a revision, it begs the question why he would say something like that. The new video download functionality is pretty gimped with the current drive sizes, they'd be nuts to keep it that way. As you might expect, I think he proves me right by, err, defying common sense just to minimize the sales impact from those who'd decide to wait for the revision if they knew what it adds and when it comes to market.
If they care enough about that to go on record with a denial, you bet it amounts to some money.