They won't make it to 5.5mil. As ppl said, they shipped 3mil meaning that retailers need to sell around 400k more units before they start asking for more shipments.
You know their is no chance when Nintendo themselves had to lower their forecast. It seem to NEVER fill their forecast lol, always coming short, so I would'nt be surprised if they fall short again with their 4mil. But 4mil is possible, if sales keep that way their is no chance, but I expect sales to pick up abit when Rayman Legends and Lego City comes out.
Then will they ship 2.5 million before April 1st.
And yeah, Nintendo always over estimates their success, but still get really successful numbers despite failing their own expectations. (just compare to other console sales during same point of Life Spam, LOL)