Well, the storm beginning ET just prior to landfall can be both good and bad, depending on where the track actually ends up going. The predictability of where the worst effects of the storm will be felt inherently goes down during ET given the transformations occurring within the storm. Specifically, where the strongest winds are moves outward from the center of the cyclone (even though their intensity may decrease) while the outer wind field actually spins up. The storm should be moving fast enough that precipitation amounts aren't too much of a concern, but that's not all good. Instead, this could enhance the potential for high waves to the east of the center, particularly given the intensity of the storm. You see this a lot with ET events, but also to a lesser extent with intense hurricanes accelerating to the north -- think, on a lesser scale, what happened with Dennis and Katrina last year. I'm not saying that will happen here; just something to watch out for. Needless to say, Hong Kong certainly wants to end up on the western side of the cyclone, as the impacts of most transitioning storms start to become even a bit more exaggerated toward the right (here, east) side of the cyclone.

A couple of interesting aspects from a scientific perspective...
1) SSTs all the way to the coastline are at least 26C, not necessarily sufficient to maintain a super typhoon but not enough to bring about any substantial weakening either (given the projected forward speed). There is a pretty sharp SST gradient from here on out, though. Also, as it moves northward, it'll be encountering increasingly strong shear associated with the midlatitude westerlies; this coupled with the SST gradient is likely what is resulting in the model predictions of ET.
2) The record low latitude for an ET event in the Atlantic is held by Michelle in 2001, which started to undergo ET around 20-21N and completed it in the 27-28N range. Looking at the model consensus phase evolution for this system, it looks like ET is projected to begin at about 21-22N and complete anywhere in the 25-27N range. I don't know what the record for the NW Pacific is, but it's not likely to be much further south (if at all). The S. Pacific and S. Indian Ocean are different; ET occurs around 20S quite frequently in those basins owing to the penetration of midlatitude troughs closer to the equator in the S. Hemisphere.

It's going to be a tight one for Hong Kong here over the next few days. Here's hoping for the best for everyone in the region.