Nvidia hasnt made an official announcement yet, so that statement has no ground as of now.
That being said, GTX 780 will have a much better price/performance ratio compared to the Titan, just like 7950s in comparison to 7970s and 670s in comparison to 680s.
No dual-GPU setup with AMD's cards is advisable right now since crossfire is a huge mess in frame time tests. A driver with a fix for this is supposed to be released by AMD in July, but no one can tell how much that will actually fix the issue. And July is still 2 months away.
As for nvidia, their next gen cards are being released within this month so it would be foolish not to wait and see what the new cards bring to the table. As we know the 780 is based on GK110, which overclocks quite easily to 1200MHz (from the experience of the Titan users). So the 780 is expected to overclock just as well if not better than the Titan, especially with the possibility of lesser voltage restriction than the Titan has. Plus, if an overclocked 780 gives you the performance you need you can avoid the hassle of getting/using two cards altogether.
About VRAM, get nothing that has less than 3GB of it (assuming your monitor's resolution is at least 1920x1080). They always say that we wont need the extra VRAM and in many cases it proves to be true. But its always good to know that your card wont have any problem running a game should it require more VRAM than 2GB.
The 770, according to current rumors, will practically be a highly overclocked 680 with the Titan's cooler. But it will still be a better choice than a 680 because of the guaranteed overclocks (to ~1200MHz on stock perhaps?) and the Titan's cooler that it will come with. And if it comes with anything more than 2GB of VRAM, it will be the wiser choice as opposed to a 680 for that reason alone. So even if you think that the performance of 680 SLI will be enough for you, wait at least until the 770 is released so you know what you're losing out on if you get 680s.
If nvidia prices the 700 series cards wisely, then we're bound to see a price drop on 600/7000 series cards. So you win if you wait, whichever card you buy.
So those are all the reasons why I'm supporting waiting for the 700 series cards and am against buying current gen cards. Since you're spending quite a lot of money on GPUs, make an informed decision. Remember, knowledge is power.