This one of the low competitive yet promising idea for starting a new blog.
The number of articles will be relatively low regarding new technologies, its features and other related in depth articles.
It can be related to 5G, 6G, Air to Fuel, Driverless Cars, Home Delivery Drones etc. You can start this as a multi topic website or single topic. You can decide it based on your comfort level in creating new articles.
An advantage of this niche is that even if you fail to get enough traffic from your blogs now, as days passes by and as these technologies become more and more popular. So in future, your blog will become more relevant and visible. So it will be a future proof niche.
Some other examples for upcoming technologies that you can think of are: Official Ad blocker by Google, Blockchain, Hyperloop travel technology, Agricultural Robot, Flexible Display.
Any other promising technologies that is expected to be active in 2019 ?