Might make sense for simplifying manufacturing and motor control if all versions have 2 motors in back:To be clear - there will still be a $39,990 RWD Cybertruck, but it will have 2 motors on the rear axle.
'Tri motor' = Plaid powertrain
'Dual motor' = Raven powertrain (plus 2nd AC motor in back)*
'Single motor' = Model 3 RWD powertrain (plus 2nd DC motor in back)
* or maybe Model 3 AWD powertrain (plus 2nd DC motor in back) - might cost less to make but less energy efficient?