Love my REI Headwinds pants, too, and was actually thinking of buying another pair. They're not currently listed on the REI website so you're probably right ... they've phased them out. I bought a couple of nice cycling jerseys at REI last summer and they disappeared from their website, too.
Will they be replaced by a new (and maybe better) Novara product later? Who knows? Maybe we'll just have to buy a similar product from a different vendor (and probably at a higher price).