Looking forward, Sony expects to ship 16 million this fiscal year (calender year shipments should be right around that mark as well).
If Sony wants to get the shipped/sold difference back into the 1.5-2 million range than we can probably expect sales to be more like 17-17.5 million.
We can use last FY's results to estimate how many of those 16m units forecast will be shipped this calendar year
Last FY only 13% of Shipments were in Q4, so that would mean out of the 16m forecast for this FY, 13.92m would be this calendar year.
So 13.92m (April 1st - December 31st) + 2.5m (Jan 1st - March 31st 2018) = 16.42m Shipped this Calendar Year.
Aiming for 1.5-2m on shelves means 17.3-17.8m sold this calendar year, so only a small difference from yours.
Though I expect the forecast will be adjusted up, just as it was last year.