Let's say Tsar Nicholas I doesn't send his armies against the Ottomans in 1853, due to him not feeling as confident in protecting his flank as IOTL. Perhaps this is due to a more active Austrian Empire sitting beside him, perhaps an earlier united Germany (1848), perhaps its simply stronger threats of a British and French intervention; regardless the war never happens.
The war is considered one of, if not the, first 'Industrial War' as it saw widespread use of railways and the telegraph, as well as modern battlefield medicine, trenches and blind artillery barrages, and was one of the first wars to feature war correspondents. However the war also showed the many flaws in the militaries of the both sides of the conflict, and led to great reorganizations of both the Russian and British armies.
So what are the short-term and long-term implications if the war is averted? And what if a war involving Russia breaks out a decade later, during or after the January Uprising?