Star Trek: 10 Things We Now Know About The Temporal Wars
5. Future Guy
Enterprise's pilot episode introduced the shadowy character from the future who guided the Suliban cabal. His identity, despite years of rumours, was never confirmed on-screen. He was shown to directly interfere with historical events, most often in a way that hindered the Federation.
This was not always the case, which supports Brannon Braga's assertion that had Enterprise received a fifth season, the 'Future Guy' would have been revealed to be none other than Jonathan Archer, in the future, attempting to change the past.
This would have enormous ramifications for the franchise, as the revelation that a primary protagonist had seemingly turned evil was shocking. The technology to affect time could not have come from the 22nd Century, so it is likely that Archer would have traveled into the future. The Temporal Wars are said to take place in the 26th, 29th, 30th, and 31st Centuries, so he easily could have traveled to any one of these.
His exact motives remain a mystery, as Enterprise came to a close before this could be explored.