A significant expansion of ISIS in Libya, or an outright takeover would eventually lead to a push into Chad and a possible linkup with Boko Haram forces operating in Nigeria and northern Cameroon.
ISIS and Boko Haram will eventually merge. I would not be surprised if the Pakistani Taliban, Afghani Taliban, and one by one, the various Al Qaeda branches eventually declare allegiance to ISIS.
A Sunni/Wahabi/Sufi ISIS spreading from Africa to South Asia, and going to war with Shia Islam, Israel, and the West is not an impossible idea to fathom.