In an article at Foreign Affairs that’s not behind a pay wall, Barbara Elias-Sanborn (not behind a pay wall) explains how the reported death* of TTP (Pakistan’s Taliban) head Baitullah Mehsud might result in the TTP announcing its loyalty to Mullah Omar, Afghan Taliban head. Thus would the two Talibans become one (to some extent, anyway).
She also writes:
TTP militants may eventually flip in favor of the Pakistani military [which] would likely grant the TTP operational freedom across the border in Afghanistan as long as it suspended violence against the Pakistani state.
… even an agreement along those lines might be short-lived: one effect of Pakistan’s double game — supporting U.S. interests in Afghanistan while surreptitiously sustaining Afghan Taliban elements — is that both the country’s U.S. allies and its Taliban ones mistrust it.