Going by your essay, it does seem like you have put in a lot of effort into writing as well as marketing. The book is out there to be sold. Many readers who loved this book, might actually be waiting for your next book. You can’t possibly disappoint them saying that you are busy marketing the first one and that you haven’t even thought of the second one! Write on….The first book will sell, the second book would do better, subsequent books would give you the title of an established writer. For all that you know publishing companies might be knocking on your door, begging you to take their contracts. You seem to love writing. Go for it! Good Luck and enjoy the writing process.