As an owner of an iPad 1, I will definitely consider upgrading because of the slow response time of my current iPad. Technology is all about speed and my Samsung Skyrocket runs circles around my iPad 1. So if the iPad 3 upgrades to a quad-core processor, better display, etc. then I can see the value in upgrading.
Here is an neat infographic on the rumors and who might consider buying the iPad 3. (via)
Source: AYTM Research