I read that the driver's were 'slightly' modified W7's. But I think anyone who believes JL just whipped up some W7's with an extra inch of excursion are only kidding themselves. If JL could build a workable W7 with 4" of excursion, they'd have released it as a W8 already. W7's are very intricate designs, it would be pretty involved to redesign it for an extra inch of excursion. Not saying its impossible (far from it), but I think if they'd have done this, they would have done more than quietly stuck it in a home audio cabinet, and nothing else.
From the things Ive read, the W7's were only slightly modified to better fit the home audio environment. I haven't read anything that said specifically what the changes were to the drivers, but I think if they'd have done that extensive of a redesign/rebuild, adding another inch of excursion, they would be advertising this, possibly as a new line of driver.