I think the lower traffic is a blessing in disguise. We currently have questions that don't get answered; if we had 5x as many questions people would get a bad experience here.
As a former founder and CEO of a company that grew ~1750% over 5 years I learned that fast growth creates an entire set of problems that can be summed up metaphorically with the phrase "Like taking a sip from a fire hydrant." Better to let it grow slowly so we can manage it. At first I encouraged every newbie I met to come here but honestly now I'm become more selective about recommending it so as not to get us overwhelmed.
Let's not be so concerned about getting traffic up quickly; chances are we won't be able to handle it. Instead we can focus on doing our best to answer each question we answer in as thorough a manner as possible so that when people see answers they say "OMG this site rocks!" With 5x more questions we'd be doing our best to provide simple answers or leaving too many without answers, at least right now.
BTW, I participated in the moderator chat yesterday and asked the question "Should we be concerned?" and the answer was a definitive "No!" Robert said "Just keep creating great content and it will work out." Most specifically he said that they plan for ALL current sites to make it.
So it sounds like the worst thing we could do is to create short, curt one line answers that require the person asking the question to do 90% of the work in formulating the answer. I think SE would be much more likely to close the site if most of our questions get trivial answers vs. not having enough users on the site. Remember, SE is search engine optimized so the best they we can do is create great content. Time spent in meta worrying about it is just time we could have used answering more questions.
After re-reading some of the blog posts and Area 51 and one thing we could each do is review the answers given by users who have less than 200 points and see if they have asked any good questions or left any good answers that have been unrewarded with up-votes. If so let's leave them a positive comment and upvote them in hopes to encourage them to be more active? (I don't mean to suggest we upvote things that don't have merit just to make sure we recognize those that do.) This will at least help us with getting more active users on from those who have already started to participate.
Just thought I'd mention that one way we could help would be to monitor the feed for the WordPress Tag on StackOverflow with something like Feed My Inbox and to start answering questions nobody else is answering like I did here:
Note how at the end I did a P.S. that said to consider asking the questions here because we are more active answering questions on the topic of WordPress. The more single-answer questions we get on StackOverflow that mention posting here the more I think we'll get people to realize that coming here to the specialists to ask WordPress has benefits over asking their question on the generalist site because I'm sure many more people will see those besides the original poster.