Absolutely, that is possible too. I guess at the end of the day two options are better than one. If people are getting tired of waiting to find a 680, and/or the 670 does indeed perform "close enough" to the 680/7970 people will jump on it.
Pretty much why I'm waiting on it TBH.
Oh and according to Gibbo, plenty of cards in stock for the 2PM launch too:
Originally Posted by Gibbo
2pm, plenty of stock to go round too.