After many delays, the Falcon Heavy rocket is expected to make its maiden flight in the final quarter of this year. The rocket uses a total of 27 Merlin engines and, at least on paper, it can lift over twice the payload of the Delta IV Heavy. It will be the most powerful operational rocket in the world. Falcon Heavy will not only be able to deliver larger payloads to low Earth orbit (LEO) or geostationary transfer orbit (GTO), but will also be able to launch 16,800kg to Mars.
Keep in mind this rocket is hasn't been tested yet so the maiden flight may be quite a bummer. Musk recently warned the chance of a successful test flight is low and said he would consider it a win if the rocket doesn't destroy the launch pad.
Half a year ago, SpaceX announced they received an order from two very wealthy private individuals for what would be the first privately-funded crewed mission beyond the Moon. At the time, SpaceX provided a planned launch date of Q4 2018 for this free-return trajectory mission.