It depends on your method. What you’re getting at here is the balance between promotion and just writing the next book. That’s a balance authors have had to work with for decades, if not centuries—the idea being that promoting your book keeps it in people’s minds. Right now you can do that through engaging blog posts, being on Twitter, going to conventions, doing book signings, and all of these things. They take time. If they take so much time that you’re not writing your next book, then the question becomes are they worth it?
Do you want all your eggs in one basket? Do you want to write one book and then spend the whole year promoting it, trying to get it to take off, or do you want to, in that time, write three books and try to get one of the three to take off? I don’t think there’s any right answer; they’re both valid ways to go. You could end up writing that one book and, with your promotion, turn it into a big success that builds a name for you. Or you could be in hindsight wasting your time promoting it when it never ends up taking off. On the other hand, having three books that sell ten copies each is really not that much better than having one book that sells ten copies.
So you have to find the right balance for yourself. Part of the question that I would ask myself is, are you an engaging blogger? Can you write interesting things on a topic and build a platform that is not just about “Buy my book!”? Would it be something interesting and fun for people to read on their own, and can you leverage that to make people interested in your writing? If you can, then blogging would certainly be helpful to you.