Single world language is a great thing, and I don't care if it's Spanish, Chinese or (most likely) broken English. We will get much better science when everyone can instantly read everyone else's research. With that come huge tangible improvements to our lifestyle, like clean energy, high yield/nutrition crops and cure for cancer. Next, wide access to world news and entertainment will reduce armed conflict and increase people's demands on their own governments. Even non-political soap operas invite the question of "why the frak can't we live like this".
Once we are done with language, I think we will end racial conflict by ending race. This is well underway in SF Bay Area. Nobody under the age of 30 really cares. After a few generations of gene mixing, there will be no large homogenous groups that can gang up against others.
Oh sure, there will be holdouts. I envision pure Caucasian villages in Wyoming where conservatives can, with full public support and protection, practice their indigenous hunting, armed self protection, petrol-based lifestyle, "traditional family" culture and religion. They will probably refuse government-provided healthcare in favor of homeopathy mixed in whisky and enjoy booming trade with Amish.