Interesting! Without Socrates, Xenophon develops a more scientific method earlier on (if I understand what Nichomacheus is hinting at). Emphasis on the necessity of evidence and reasoning from proof? Aggressive and constant questioning of an opposing thesis? Such a method is much more empirical and skeptical in its nature. That sounds a lot like modern empirical science! A move away from the mysticism of Pythagoras (whom Xenephon disagrees with) and Plato (who IATL never delves into philosophy) and the a priori rationalism of Aristotle (who would likewise be butterflied away as a philosopher) means a greater emphasis on empiricism and skepticism. Would an earlier scientific revolution result?
Also, how would political thought be different? Presumably much more progressive!
Actually, I was thinking that the Xenophonic method wasn't all that different from the Socratic method, since the Socratic method entails questioning and reason. I doubt Xenophon gives this a scientific edge (OTL it took Aristotle and then the scholastics edged out empiricism in his work). He would probably use the method to discuss ethics, his primary interest OTL. Most likely, his ethics are if anything less revolutionary / provocative than Plato's. Importantly, though, Plato is side-lined as a playwright, not a philosopher.
It's unclear how much Xenophon and Plato agreed about methaphysics, but I'd guess that the former was very down to earth. If anything, Xenophon's politics are almost certain to be less progressive than Plato's / Socrates, but with unsure results. Firstly, Xenophon is normally associated with a fairly aristocratic outlook, but an Athenian aristocratic view. He stil lionized Sparta (in the Hellenica, for example), but I can't seem him holding forth on the necessity for the property-less guardians and so forth. Nor can I see him denouncing ancestral gods easily.
Since Plato has been side-lined, however, further thinkers might come along that would push greek philosophy toward a scientific empiricism. I'd imagine that if you dovetailed OTL's Aristotle (who's probably buterflied in the ATL I outlined), with TTL's Xenophon this may be the result. Even then, though, it might not be: Greek thought tends not to empirical compared to later work not because of its methods but because of its preferred subject matter, ethics, metaphysics, and theology, and because of the lingering theistic elements due to the tenor of Greek society.