Don't say Japan, Japan is literally the worst place for the PSTV, and as this generation has proven, the worst market to compare to America.
I've seen a whole bunch of claims that the PSTV will flop with little reasoning, people had stronger justification for the PS4 being a flop before it released.
I was catiously optimisitic when they announced it as VitaTV, and I'm cautiously optimistic now. Its cheaper than the 2DS, has a library that basically dwarfs this gen and last gen, cheapest way to get remote play if you have a PS4. Its the perfect entry console and can easily be a side console if you haven't played in the PS ecosystem before. Other than the motion controls that set the Wii off, it basically is set up just like it, and Sony typically doesn't have the advertising issues for them to market incorrectly here in the states.
I can't predict another PS2/DS/Wii but I don't understand how some people are can be so certain its will flop.
In this day and age, with the Internet, ignorance is a choice! And they're still choosing Ignorance! - Dr. Filthy Frank