The death of Mullah Omar and the emergence of the Islamic State has changed the insurgent (terrorist) landscape in Afghanistan. The Taliban seems to be in competition with the Islamic State; as is al Qaeda. The relationship between the Taliban and al Qaeda would seem to be strengthened over the past few weeks based on some of the "press releases" sent out on behalf of the two groups. Read "Taliban Chief, Facing Struggle for Power, Welcomes Al-Qaeda Alliance", Radio Free Europe, August 15, 2015 and "Al-Qaeda Leader Declares Loyalty to New Afghan Taliban Leader", Radio Free Europe, August 13, 2015.
There are lots of conspiracy theories floating around in the news and on the Internet (some people think those two items are the same). One theory is that the Pakistan ISI is purposely fragmenting the Taliban while putting forth the facade of trying to unit the Taliban in an effort to advance peace talks. Another theory revolves around the al Qaida - Taliban endorsements. Read more in "Complex Conspiracy Theories Shadow al-Qaida-Taliban deal", Voice of America, August 14, 2015.