I think if that crossover was going to be taken seriously (hopefully as an alt. future and not literally what happens), the 2029 date for the first RoboCop would have to be taken. I think RoboCop's main timeline would have to be one of the many spin-offs from Terminator 2. I guess a personal theory could be that, after the time travel in the original RoboCop versus The Terminator comic, that original dark future continued on (split timelines - Marvel logic), with Skynet eventually killing every human on the planet, and RoboCop of this dark future going back in time and creating another timeline where, uh... John Connor gets beheaded, lol.
So, basically, in the RoboCop/Terminator timeline:
Timeline 1
2029 - Terminator: Resistance
Timeline 2
1984 - The Terminator
1995 - Terminator 2: Judgment Day
2030 - RoboCop
2031 - RoboCop 2
2035 - RoboCop: Rogue City
2036 - RoboCop 3
206? - RoboCop versus The Terminator (Dark Future)
21?? - Terminator/RoboCop: Kill Human (Dark Future)
Timeline 3
1984 - The Terminator
1995 - Terminator 2: Judgment Day
2030 - RoboCop
2031 - RoboCop 2
2035 - RoboCop: Rogue City
2036 - RoboCop 3
2036 - RoboCop versus The Terminator (RoboCop Assassinated)
Timeline 4
1984 - The Terminator
1995 - Terminator 2: Judgment Day
2030 - RoboCop
2031 - RoboCop 2
2035 - RoboCop: Rogue City
2036 - RoboCop 3
2036 - RoboCop versus The Terminator (Main Events)
Timeline 5
1984 - The Terminator
1995 - Terminator 2: Judgment Day
2030 - RoboCop
2031 - RoboCop 2
2035 - RoboCop: Rogue City
2036 - RoboCop 3
2036 - RoboCop versus The Terminator (Skynet Erased)
Timeline 6
???? - RoboCop versus The Terminator (Dinosaur Crushes Terminator)
Timeline 7
1984 - The Terminator
1995 - Terminator/RoboCop: Kill Human (Main Events)
That's just a theory though, and I have no idea how the many RoboCop/Terminator video games could fit.