The decline is likely to continue as all consoles are likely to be down, the only positive is that Wii U will no longer be sold so its successor will increase HW in that market. I would say the same for Vita, but no successor exists so that market is going to completely die.
Should be noted most hardware losses is due to the fall of the handheld market and Wii to Wii U.
MS loves to spout XB1> 360 in same timeframe and PS4 is obviously > PS3.
So unless the Switch takes place of the 3DS+ Wii U+ Vita, hardware will still probably fall. It is unlikely as Nintendo likes to keep profit with its HW.
I be more pessimistic
PS3/360/Wii U-500k combined
Vita-about 1 million
3DS-3.5 million
XBO-7 million
PS4-15 million
NSW-9 million
Total-36 million
So I guess the losses might stabilize, depending on Switch performance. Which is pretty much unpredictable.







