I wouldn't hold my breathe if I were you. Both are typically 500kg heavier than a (ok, the shorter 10.1m version) E400 - the latest London-spec E400 weighs less then 11,600kg empty, and the Scania weighs 12,100kg. Even the latest B9TLs in London - supposed to be lightened, are slightly heavier than the Scania. That extra weight will take a penalty of 9 people in capacity, put it this way. The flip side is this HK version of the E400 has a bigger engine, and being longer as well, should be heavier if it was built to the same body spec to the UK 10.1m version, but I don't think it would close the gap much.
Taking the weight issue aside, the Scania's chance is slim, simply because I can't see ADL would offer the bodywork on it for competition reason, and Optare is unlikely to make it here as it has no customer base here, and then the Omnicity version is simply more expensive (supposedly).
For the Volvo, unless Wrightbus somehow find a way to build all the extra bits (air-cond and so on) without taking up as much weight, or simply find ways to reduce the weight further, it is not likely we'll see the 2-axle Volvo/Wright combination either.
