I would say if there is an iphone 5, it could only be launched next year since iphone 4 white colour is still not available yet till late this year.
well so far four years in a row the cycle of release has beent he same, announced first week in june released in july up to september in other countries.... so its safe to say the same will happen next year also, i doubt apple will stop but you never know. nothing is ever 100% with apple. but imo its very likely