The “Core Support” for ColdFusion 10 ends on May 16, 2017. That means, no more Security patches/updates by Adobe for this version of ColdFusion after mid of May 2017. The detailed timelines are mentioned here in the EOL Matrix.
What is Core Support then? Core support is the time frame wherein the product and the support programs are available. This provides, five years of product support from the general availability date of a product.
General availability is the date when the product and the support programs are announced and available for purchase.
Extended support provides an additional two years of Platinum Maintenance and Support(M&S) services after the end of Core Support. Extended Maintenance and Support provides the extra time you may need, to plan your migration to Adobe’s latest technology. Here is the source.
So, if you are on version 10 or prior then, its the correct time for you to upgrade. This will ensure your eligibility of getting Security updates and patches timely from Adobe, for the supported versions of ColdFusion, as and when released.