Not sure about 55km, but if he is on form and peaking properly, i can’t see any reason on earth why he won’t smash the record.
He’s one of the best time triallers around today, maybe in history (although how you tell that given equipment advances, it’s difficult to quantify*). He’s got a proven heritage on the boards. Given Voigt, Brandle, Dennis and Dowsett have all added another 1/2k each time, and with the utmost respect to them they aren’t really the same league as Wiggins when it comes to TT, fine riders as they all undoubtedly are, I reckon at least another 1/2 on top of Dowsett, wouldn’t be surprised to see another km which puts him around 54, and from there – 55, well why not?
* although making them race round a fixed oval on a bike that’s basically the same design and technology as the ones used in the past goes some way to regularising it.