There is already a pan-continental war happening at large scale in case you haven't noticed; it comprises a mix of information warefare and cyber attacks.

Further conventional wars are to be expected, too: some people speculate that they will be about access to clean water (in the past, borders/owning land areas were more often the motive behind armed conflict). Current tensions of this kind can be observed e.g. between India and Pakistan, although they have not escalated.

Questions about the chances of a world war should specify the time range to be complete/meaningful.