It has been reported from sources close to Nvidia that although most partners are ready and waiting for their new dual-GPU card (rumoured to be named GTX 590, based on two GF110 cores), Nvidia want to wait for AMD to make the first move.
AMD's Radeon HD 6990 (code name Antilles) is currently set for a Q1 2011 release, after all the top end single-GPU cards have been released. We recently saw that AMD have delayed their top single-GPU card, possibly to allow them time to respond to the current fastest single-GPU card, the GTX 580. Is Nvidia now doing the same to AMD? It certainly looks like it - Nvidia wants the overall performance crown so we should expect a close battle come Q1 2011.
An image of the work in progress reference design for the dual GF110 card. Note there are quite a few components missing: