All FSDs include the free HW3.0 computer swap regardless of the time of purchase whether you bought FSD in Oct 2016 or now. FSD is not going to work without the new computer that is 10 to 20 times more powerful. In the podcast
here, Elon explains that FSD software would be too complicated if they tried to make it work with the current hardware but he said the new hardware will enable 100 frames per second without any compression.
What is not clear is whether Tesla will upgrade components other than the Autopilot computer which is easy to swap according to Elon. AP2.0 has black and white cameras whereas AP2.5 has color cameras. Sentry mode, dog mode, and dashcam features don't work with AP2.0. The question is, will those features start working when you get the free hardware 3.0 upgrade if you have AP2.0? That part is not clear. However, you will definitely get the new Autopilot computer if you have FSD because FSD features won't work with the current computer.