They must have had some plan as to where and how the empire was going to grow and how the relationship between the colonies and the UK would evolve. Are there any books that detail the future plans of the British Empire?
I'll attempt to answer the question with regards to where the empire had come from in the previous years, it's difficult to say whether the tensions in Europe would have reduced as it is widely regarded there would be a European war anyway. But i'll attempt to answer as if peace remained in Europe.
Throughout the 19th century, the white colonies began to drift towards becoming independent nations. Canada gained its own representative legislature, with the ability for self-governance, with the exception of foreign relations, in in 1868. With the Oceanic colonies of Australia and New Zealand following suit in the early 1900's. Dominion status was formally introduced at the 1907 Colonial Conference. These self-governing privileges set the tone for independence movements throughout the empire, more prolifically the bid for Irish home rule throughout the late 18th and early 19th centuries. The gift of self governance to the Canadians was as a result of political unrest in the region, the Durham Report of 1839 mentions that the only was for continued loyalty to the crown, was self governance.
"It is not by weakening but in strengthening the influence of the people on their government, that it will be possible, in my view, to bring about concord where discord has so long reigned, and to introduce a hitherto unknown regularity and vigor into the administration of the provinces."
Self governance was supported by the people of the Canadian territories, Joseph Howe, a member of the assembly, wrote to the Colonial Secretary supporting the Durham report:
"We must hasten," wrote Howe, "to bring to the colonies the principle of self-government, a government accountable to the people. It is the only straightforward and certain solution capable of curing a deep rooted and far-reaching affliction."
Without the First World War, it's pre war territories would most likely be its largest extent. post Boer War, Britain ended its European neutrality and removed itself from its Pax Britannica, and entered the great game of alliance within Europe, allying itself with the major players in 1907 forming the Triple Entente and ending territorial disputes with a number of countries.
By this point in the imperial period, the territories of perceived worth had been divided between the great powers, and the technological advancements in weaponry and industry, therefore made it unviable for Britain to become embroiled in a colonial war of an industrial scale, especially with the main powers engaged in an intricate web of alliances and mutual support agreements.
With regards to the relationships between Britain and the Colonies, these are entirely dependent on the location and population of the territory, as well as the worth to the British economy. For example, the British would be far more interested in maintaining good relations with India than it would be with the Sudan.
With the European powers being militarily and industrially prominent when compared to the Ottoman empire, which at the dawn of the 20th century, was merely a shadow of its former self, Would probably highlight the area for future expansion for the European empires. The growing need for oil, for both military and civil reasons, was just beginning to become recognised as a fuel source of the future in the early 20th century would make the region a hotspot for conflict. The Empire would gradually begin the process of self-governance within a system which is better explained as an empire/commonwealth hybrid, with independence for dominions and the beginnings of the process for non-white colonies, but remaining under the same foreign policy ideas.
Unfortunately I was unable to locate any sources specifically detailing the future plans of the empire, but I hope this answer is of use to you!
Any follow up questions are welcome.
Sources:
Bell, Duncan, The Idea Of Greater Britain: Empire And The Future Of World Order, 1860-1900, (Princeton: Princeton University Press, 2009).
Harris, Arthur T., Empire, State, And Society: Britain Since 1830, (Chichester: John Wiley And Sons, 2012).