The CD3mkII is discontinued. The CD5 is just coming out now. Yes it will have the same top loading transport as the CD3mkII and CD7.
The new CD5 is more of a clone of the REF CD7 but uses FETs in place of vacuum tubes. Remember, the CD3 was designed over 7 years ago and the mkII did not make any major design changes but benefited from resonance control through extensive strategic damping and some parts upgrades. The REF CD7 was a completely new design based upon the REF3. This resulted in dramatic sonic improvements over the CD3mkII. The CD5 should much more closely resemble the performance of the REF CD7 only with a solid state twist.
I think its also important to remember that the digital portions of these pieces are basically the same. It's the power supply and analog circuitry that makes all of the difference.
I am an ARC dealer.