What skills would you suggest I focus on?"
Great to hear you're thinking of showing up. There's certainly a lot of skills that are helpful for a hike like this. I feel a bit weird even offering advice on this because I have so much learning to do myself, but I'll try to share a bit of what I've learned.
A basic competency in some skills is pretty much essential (ie. navigation, clothing choices), while others skills can be quite helpful but if you lack them then you can compensate with your gear and route choices (ie. packrafting, river fording etc). So considering which skills are essential and which ones are optional may help illuminate the best areas to work on. As an example, I made the choice early on that I wasn't going to packraft the 2012 BMWO because I lacked the paddling skills, familiarity with the local rivers and cold weather paddling clothing to do so safely. I could have working on developing in these areas, but I chose to focus elsewhere.
Navigation and cold/wet weather clothing choices are two skill areas that are pretty much required. You don't need to be the best navigator (I'm certainly far from it) but you need a basic competency and then you can work from there. If you're so-so navigator, you may be able to account for that with your gear choices (ie. altimeter, gps) and route choices (ie. simpler terrain). Knowing basic skills like map/compass is essential. This is one of the areas I want to improve most upon for 2013. Here's a good website with info on this:
Cold/wet weather clothing is another important area. To some degree you can account for this by taking more clothing, but it's ideal to get your clothing selection refined. I was very happy with my clothing choices in 2012 (see gearlist in my profile) but the weather conditions could be wildly different next year and each person is different both physically and in their hiking styles.
Knowing your own body is another skill/knowledge area that is pretty important. On one hand it's interesting to push beyond what you've ever done before, but it's still good to have a decent idea of how your body is going to respond. Knowing how many hours/day you'll be able to hike and how much sleep you need affects other choices like food, clothing and sleeping equipment. I'd recommend doing a couple high milage one nighters in advance.
Other helpful skills include snow travel, grizzly encounters, water crossings, avalanches etc. You can make choices to minimize your exposure in all of these areas though. For example, Stadler and Larch Hill passes have quite a bit lower exposure to avy risk than White pass.
Snow travel is one of the toughest areas to really plan for this far ahead. The route was do-able without snow shoes last year, although they were certainly handy at times. Taking some small/light snowshoes (ie. a kids model) like Dave C. did was probably the best snow travel choice in 2012.
I'd recommend picking up the North and South halves of the Bob map and getting familiar with the general area early on even though the start/finish points haven't been finalized yet. It doesn't sound like they're going to change too much though, so you could put together a few possible routes and perhaps come up with a tentative strategy from there and start to mull over aspects like snow travel, water crossings/travel etc.