The bayonet and the cult of the offensive would probably still be very popular. Cavalry would definitely EVENTUALLY die out, becoming more of an honor guard type.
No tanks, no advanced aircraft or advanced machine guns. No superior infantry tactics, just an overwhelming mass of bodies. Hand-grenades still very basic.
Your still going to have a war in the future and when it happens its probably going to be a lot more bloody.
Offensive yes, bayonet no. There was a transition in military circles at the time to great emphasis on firepower. Shock action was becoming obsolete and the traditionalists were aging and falling out of power. As firepower becomes more developed and light machine guns and auto rifles are created, the bayonet loses lots of its luster and usage. Fire and maneuver tactics existed prewar, but were not uniform. Given until the 1920's there will be an increasing tendency toward firepower over shock. Remember even the semi-auto rifle was being developed prewar by every major power. Maybe with new leadership this weapon is given greater emphasis.
The POD is going to be somewhat important here, as if the solution is just that Franz Ferdinand does not get assassinated, there will be another Balkan conflict, as the AH empire is going to eventually come down to civil war when he rises to power. Even if he doesn't, on a longer enough TL the AH empire is likely to enter into an internal conflict: if not in 1917 then certainly in 1927. This will mean that a modern conflict of larger proportion will happen in Europe for the major powers to witness. Perhaps it will point the way to the future conduct of warfare. Or not. But I think more conflicts on Europe periphery are coming, which can further influence the debate.
The trend was toward motorization and military aircraft development. We might end up seeing a less refined version of "Blitzkrieg" with motorized units becoming the new arm of maneuver and enhanced aircraft backing them up. The cult of the offensive is still going on of course, which means pushing hard. It was not necessarily an incorrect doctrine, rather, it was somewhat out of place without radio and motor/mechanization. Without the means of decisive maneuver it is really rather difficult to effectively fight an offensive campaign.
Edit: With more advanced radio types (this is coming as there is both a civilian and military demand for it), motorization, lighter machine guns, and increased aircraft range, size, and firepower warfare would certainly be more like the 1930's but without the practical experience of making it work properly. Infantry would still be the queen of the battlefield and there would be far fewer and more experimental AFV's than historical, but there would be many more people alive. People that survive and go on to enter into the sciences and other fields might drive technology more than we are able to imagine. Though many of the developments are likely to be in pure science than military science, there is likely to be enough that changes the nature of war.
Much of the adoption of new technologies hinges on military commanders willingness to look forward. Many militaries were trending this way, including the French, German, and Austro-Hungarian, though all remained mired in outdated methods and technologies. Some, like the French and AH were hamstrung by budget constraints, though this was easing for both. By the 1920's there are likely to be retirements in all major parties which is likely to open up the field. However, there is also the issue of increasing industrialization. This will matter most for Central and Eastern European powers, who were just starting to make up the gap between the West and East. This will have a huge effect on planning for war, as each major power is able to better equip their forces and supply them beyond what was possible in 1914. It is also likely then that the major powers are going to start planning for longer wars and to circumvent blockades. Germany was already working with that in 1914 before the war, but the studies were only in their infancy. By the 1920's there might very well be better planning for this eventuality and stockpiles of crucial resources in case of war and blockade. Perhaps the Central Powers are going to be better able to resist, though with increased capabilities for Russia, which has had time to economically develop.