I highly doubt it. At least for the T series.
Compare the picture of the new T430:
With that of a T420:
On the T420, there's a recess in the keyboard bezel, between the "Escape" amd "Print Screen" keys, where a part of the keyboard (which includes the volume and power buttons) goes underneath the bezel. Also, the connector is probably different, or at least has surely been moved around with the new, different chassis.
@JDay: Like I said, the keyboard bezel is different. See for yourself (that's a T420):
The bezels on the T430, T530, etc. don't have any recess and are uniform at the top where the keyboard is inserted. Even if everything else was the same, you'd have to cut the new bezel on the T430 to accomodate the old keyboard.
And I've had confirmation the screw layout is different. The chassis for the T430 is a whole new beast. The guy couldn't confirm me for the connector, but it's presumably different to support those keyboards that will feature back lighting.
Something noteworthy: The T430 used for the official press shots has a crooked keyboard upper-left corner and Escape key. I wonder how they managed to do that (the upper row is meant to be higher than the others, but not like that). It's bad enough to have lost a row and be stuck with chiclet keyboards across the whole line, we better not end up having keyboards that get easily warped.
