There are still a lot of people on AGP so a DX10 AGP card make sense. However, I think Nvidia/ATI will only release low-end or maybe at the most, mid-end cards. Don't hope for any high end AGP card as the cost is more, the power requirements may not be enough and the AGP slot will seriously be bottle-necked....

If somebody has $$$ for a high-end AGP, they would have upgraded to PCI-E already!!!