The Islamic caliphate in the levant plan to give everyone that choice.
The control of Mecca in particular is what ISIS will aim for; that's the 'Dreamland' for them. Only obstacle I'd imagine, from the average muslim perspective, would be that ISIS is shown itself to be too brutal - but not from a theological, cultural or historical angle - ISIS is spot on.
And, brutality is eventually accepted by the average muslim, as part of 'what must be done', especially if practised by another perceived 'devout' muslim, as ISIS professes to be. Unless KSA shows itself to be 'holier than thou', so to speak and compared to ISIS, which is fairly impossible since the House of Saud has already ingratiated it too much with the western world.