I think the final result is that they must live in harmony with nature.
Defining this world is going to take a tremendous leap of faith to define what "no ability to think hypothetically" means at a biological level. Once we have that, we can extrapolate out to what that would mean for the species as a whole.
Of course, the real challenge is that basic thought requires some level of thinking which might be seen as hypothetical. If you eat food, your body observes inputs though taste and smell and does its best to predict what sorts of work the digestive tract needs to do. This system is so advanced that you can even get "more energy" through a placebo effect. If you think you just got more glucose, the body/mind will often permit more action on the presumption that more glucose will hit the small intestine shortly. Its really hard to live without this (in fact, by some definitions of "life," the inability to do this would prevent single celled organisms from forming). Accordingly, we're going to have to carefully sidestep this definition and find another definition of "hypothetical thinking."
The definition I find most promising is one which breaks hypothetical thinking into two parts. The first part is where we think of the hypothetical situation, such as "I wonder what it would be like to have soup for lunch today." However, at a biological level, its really hard to separate that phrase from "Soup is happening, the digestive tract moves." Instead, we're going to draw the line differently. The second part of this hypothetical thinking is the ability to discard the thoughts. If you finish thinking through what it would be like to have soup, decide "Nah, I'm having salad instead," you discard the entire mental universe you constructed to explore having soup. But what if you couldn't discard it? What if those thoughts had to continue existing as long as they "wanted" to? Anyone who has unbridled hypothetical thoughts would quickly go insane with the myriad of worlds in their head.
I don't define this line by sheer happenstance. This is also one of the accepted lines of reasoning for exploring reversible computing. In the theory of reversible computing, it's not the computation that has entropic costs, but rather the act of erasing those computations. Thus, I can argue that Homo-whavia can indeed think, as well as any reversible computer can think.
The biggest challenge with this is that reversible computing is very bad at handling irreversible changes (no surprise there). Accordingly they would develop a culture which avoids considering irreversable changes. Everything would have to flow smoothly from one state to another, permitting them to stop thinking about a "hypothetical" simply by letting it flow outside of them (to be forgotten elsewhere, most likely).
This is I think the defining characteristic of such a species. We often say "every action has its consequences." Their version would be much more extreme, for even their most secretive thought must eventually have a consequence as it is permitted to flow out of their minds into the world. This concept of everything having consequences may be so prevalent that the only phrase they can construct regarding the topic is "Consequences are." (manipulating a phrase from Stranger in a Strange Land to suit my fancy)
Such a species may survive. In fact, I'd be tempted to argue that there exist religions which actually describe such a world. Daoism believes "everything is of the Dao." The Dao flows through us, and while we perceive a separation between us and the Dao, it is believed to be just an illusion. The Daoist cultures sought long term stability. If a ruler was poor, they would not attack him head on, but allow the flow of time to erode his support until it brought him down to his proper place.
The wisest of homo-whatvia would be those which were most aware of their balance within their "Dao." That individual would be so in tune with the consequences of those balances that they might not even more perceptibly. The tiniest flickers of their hands may be enough to keep their world in tune. Any homo-whatvia would recognize that they are doing this, and accept it. However, another species, such as the impetuous H. sapiens might not. They may see the leaders of homo-whatvia as not acting at all. Homo-whatvia would do its best to communicate with us, but that language gap would be significant. They might even have to resort to strange aphorms in their language, which even then might not translate. Perhaps the best communication they could achieve would be...