Complex sentence: There have been plans at various points in history to connect Shinjuku into the Shinkansen network, and the 1973 Shinkansen Basic Plan, still in force, specifies that the station should be the southern terminus of the Jōetsu Shinkansen line to Niigata.
Split into simpler sentences: There have been plans at various points in history to connect Shinjuku into the Shinkansen network. Originally, the station was slated to be the southern terminus of the Jōetsu Shinkansen line to Niigata.