Largest SpaceX rocket will reach space not in 2017 as it was planned, but not earlier then in January 2018.
According to latest news given to public on last Tuesday by Aviation Week and Space Technology first flight was moved in time from the end of December to January 2018. SpaceX still suffers for delays with their triple-booster Falcon rocket, but fortunately managed to already schedule first test fire. It will tool place in December 2017 at LC-39A at Kennedy Space Center.
It will be first time when 27 Merlin-1D engines will be ignited simultaneously; after test fire only weeks will separate us form first launch of Falcon Heavy. It's first mission is not covering delivering any payload to orbit and SpaceX still keeps flight plan of maiden flight in secret.
Falcon Heavy is in fact tripled booster of Falcon-9 FT with its upper stage equipped with single Merling-1D Vacuum engine. Rocket is long for 70 m and weighs 1420 t. It will be able to deliver 63800 kg of payload for $90 million to LEO orbit comparing to $62 million for 22800 kg in case of Falcon-9 FT. As we can see price per 1 kg of payload is much lower in case of Falcon Heavy, what surely will help SpaceX in creating new market of heavy launch vehicles. As competition is not able to offer comparable vehicles in 2018 (for example heaviest variants of ULA Delta IV rocket are able to deliver 29 t to LEO) it is pretty sure that for some time SpaceX will get dominating position on the market a least for a while. Combined missions covering delivering number of satellites at low cost under the fairing of Falcon Heavy will surely help in getting more contracts and probably solve some problems with delayed Falcon-9 FT missions. Of course such bright future is possible only in case of success. If rocket will fail or it show significant design flaws it is possible that it will soon became interesting project from the point of view of the technique but unwanted on the market.