If you’re blogging to reach readers, and want to know what people want to hear, there are ways to gauge the interest level out there.
Some bloggers like to do long series of related posts. Certainly in this case you’re going to want to put up one or two posts to see what the interest is. This isn’t fool proof, as people don’t always consume content in real time, and the best way to establish yourself as a thought leader in a subject is to produce content on that subject. But if you post a couple of pieces on a subject and you get no engagement, you can assume you don’t have the audience for it.
An approach I think is a more effective use of time is to curate content on the same subject that you’d like to blog on. This will attract an audience on various social networks, and you’ll learn what, if anything, people want to read. You’ll also learn when to post and what hashtags to use. Once you’ve posted some 3rd party content people will expect to see content on that subject from you, and you’ll be in great shape to post content for them.