Wow! An open-ended question that
doesn't come from Banker_Frank! That makes a nice change!
If ABers can work out what 'the next big thing' in technology will be, then (assuming that we've got the necessary entrepreneurial spirit and access to some financial backing), we'll all be billionaires very soon ;-)
Most of the 'experts' in the field though seem to think that any big advances are likely to be software-based, rather than physical inventions like smartphones. e.g. see here:
https://www.forbes.com/sites/forbestechcouncil/2018/12/26/2019-tech-forecast-11-experts-predict-the-next-wave-of-breakout-technologies/#2282c39159a9
I suspect that rapid developments in Artificial Intelligence will soon see us laughing at the simplicity of devices like Alexa, with far more devices available which humans can interact with using their voices (and which are capable of far more things than, say, Alexa can do).