You know marketing and increasing hype is best for selling.
If they had advertise same product twice more earning... They present last days Titan Black with 6GB and slower than GTX780Ti and now they will launch GTX780Ti 6GB for same price with higher clock and faster... Probably only small number of Titan Black is planned. Customers need to follow they need not advertising if don't have to afford that. Example I'm glad because they didn't launch GK110 with 2880 CUDA for 1000e. For me that is enough because I need performance more than memory and higher memory clock more than quantity. I doubt I'm ready to risk 1950MHz with tight latency for 6GB and later to change card on faster before I even need 6GB memory. And I'm glad because GK110 will stay longer time actual and because NVIDIA looks like to optimize better DX11 games with next drivers. No matter on anything Project Denver will came and I will not need 4GB of Video Memory. Next monitor I plan in 2560x1440 resolution but not soon.
We beg them on knees before only 3-4 months, hundred and thousands of customers, hundreds of pages to give GK110 with 2880 CUDA and 6GB model they don't even think about that.... Maybe is better if thought to sell for 1000e.
Yes I remember people talk... Please NVIDIA, Please 6GB, we will have memory bottleneck, you will see, please AMD have 4GB... Nothing.
They sell story about expensive memory and price would be really crazy... I have GTX780Ti 99% because they decide to go with 3GB cheaper.