Well, I've pondered, and, while I agree that there are loose ends, I do believe there is a conclusion. I've found the main theme of "Taking Chances" to be just what the title infers - Colson taking a chance by walking into the Red Stallion, which sets off a series of events through which he starts to come to terms with his true self. He still has a way to go - that is clear - but by the closing lines of the last chapter he has come out to his daughter, moved to a new town, moved in with Ellery, and, for the first time in his life, openly declared his love for his man. For me, this qualifies as a conclusion.
I don't think I'd consider Colson's new job as a horse wrangler a loose end, so to speak, because he has a firm offer in hand and has accepted. Yes, it's interesting to see him working and honing his skills and we know that he's going to be learning some new skills regarding paso finos, but I wouldn't really consider those loose ends.
Of course, the search for Adam's killer and the Bill Early matters are loose ends, and they serve as a important factors in bringing Ellery and Colson closer together, and in Colson's self-discovery, but I don't consider those threads to be the main focus of this first book.
I've been bringing to mind other series of books that I've enjoyed in thinking about how "loose ends" are handled. The first series that comes to mind is the
Outlander series by Diana Gabaldon. I believe at this point there are six books in that series with plans for at least two more. These are hard to define by genre - historical novels mixed with an unorthodox romance, time travel, celtic mysticism, political intrigue and plenty of mystery. By the end of the first book, the only thing that is really "settled" is that the two main characters are together and making plans to escape to a new country, but there are many, many loose ends. And there are many, many loose ends at the end of each of the five subsequent books in the series, because we keep being introduced to new characters whose own problems become intertwined with the main characters. Every one of the books in this series ends with a cliffhanger of sorts. According to the author, one of the main mysteries, introduced at the very beginning of the first book, will not be answered until the last page of the last book.
Another series that comes to mind is the Lymond Chronicles by Dorothy Dunnett. While each book in the series takes place in a different locale with a different set of problems for the hero to overcome, the series also leaves loose ends from book to book, sometimes picking up new mysteries along the way.
I guess what I'm taking an awful long time to say is that I think there can be a conclusion
along with loose ends and cliffhangers - and I don't think that's necessarily a bad thing. And in the case of your books - definitely a good thing.
Hope that helped.

Marie