At this point it all comes down to how Nintendo treats the Switch once it's replaced.
If they keep it around for a while as a budget alternative like 3DS, 160m is within reach. If they decide to phase it out quickly like DS or PS4, it will fall short.
There's just no way to know at this point.
Regarding their 13.5m forecast, Nintendo aren't stupid; they're well aware of how aggressive a target this is and I don't think they'd be so bullish if they didn't have carefully laid plans to make it happen. They may indeed fall short, but I don't think it will be by much.