Not much doubt about it now. Speaking with Norwegian site VGTV, Sony's Kaz Hirai has confirmed that they're no longer producing 60GB PS3s for the American market, and that once that model is gone they'll be back to a single $599 model (the 80GB version).

We're no longer in production for [the 60GB PS3], so once that product is gone from the retailers shelves, then we're back to the $599 SKU only, so it's not like we have a two-price strategy here in the US market, which we found out very early on, that consumers react mostly to having one SKU as opposed to two.

His confirmation has prompted the following, clearer reply from SCEA, issued to Next-Gen, which reads:

The 60GB PS3 will be available in North America for $499 until supplies of that unit are depleted. We have ample inventory to meet the immediate needs of consumers in this territory for several months to come. We won't be making any further announcements regarding our PS3 model hardware strategy in North America until the 60GB model is exhausted and market conditions are evaluated.

Urgh. My head hurts. The Kaz interview's hosted on VGTV's site, hit the link below to check it out (it's towards the end)
VGTV Kaz Hirai Interview [VGTV]