I don't think FSD will be incremental like EAP. The "F" stands for Full. There may only be a difference between level 4 and 5.
The EAP 2.5 has much more capability than presently provided. The hacker video shows the car identifies much more than you think. It will not need lines to drive as it already defines a "driving surface" independently from "lanes" and "route". Be patient. Hopefully stoplights, stopsigns, speedlimits and intersection turns will be activated on EAP 2.5. I have a local residential street that has about a 150' yellow centerline at it's beginning. I can get to 18 mph and get the AP gray while it still sees the center yellow line and turn on EAP. It then accurately drives down the right side of the grass lined, macadam street with no lines. Last week there was a family with a baby carriage walking on the right edge of the road as we approached a short, non-elevated bridge with a sidewalk. The car recognized the pedestrians in the roadway, slowed, stopped and continued when the pedestrians got on the bridge sidewalk all with no lane markings. This is high level stuff.