In an interview with GamesIndustry.biz, SCEE president David Reeves stated that after the 60GB PS3 stock sells out the SKU will no longer be available in North America.

Reeves revealed that the 80GB SKU, which includes MotorStorm, will replace the older package. This would mean that the price cut wasn't a real price cut in North America, but rather a method to add value to the previous $599 price point..

After the 60GB stock sells out, it's unclear whether or not Sony will release a package with no game. We will keep you up to date on the "price cuts".

Update:

Apparently there has been some miscommunication, as Sony's official PlayStation blog states that the above is not quite true:

"One quick thing before I head to the show for the last day. I just wanted to clarify something. I’ve seen a lot of posts this morning related to the 60GB SKU and the comments by SCEE President David Reeves. As we announced this week, SCEA’s product offering in North America consists of a 80GB PS3 available in August and a 60GB PS3 available now for $499. We will have ample supplies of both models to meet the needs of consumers for the foreseeable future." - David Karraker, Sr. Director, Corporate Communications.

Update 2:

Reeves was actually right. The 60GB SKU is being phased out in North America. Confirmation by Kaz Hirai in video here, and also via IGN:

"The 60GB PS3 will be available in North America for $499 until supplies of that unit are depleted," Patrick Seybold,  Senior Public Relations Manager for SCEA said. "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."