Just a few years ago, there was only one, but now, each month the Team has to build, test and debug four templates a month instead of one.
Not to mention Drupal, the newest club was just launched, and they'll be a bit of caching up, and then keeping up with the current themes.
RT themes magically appear every month, along with the other club templates, but you can't imagine how much work it takes to produce templates that work each month on a monthly basis.
And as for as creating new clubs for new CMSs of forums, from the ground up it can take up to a year or so.
There also another point to consider, while Joomla, phpBB3, Wordpress, and Drupal are free, vBulletin is a commercial product which requires an initial investment of around $200 for a license.
This really forces vBulletin into niche market, before you join a template club, you need to pay for the software.
phpBB3 is free, $60 to join the club, Total $60 to get a matching template for your site.
vBulletin is $195, $60 to join the club (if one becomes available), Total $255 to get a matching template for your site.
While you may think it's worth it, many members man not.
Quite often when searching for a component, members will ask what we suggest, when we give them links to commercial components which we feel are better tan the free ones, even if they only cost $5, $10, $20, they reply, 'I have no money', or 'I want a free one'.
So, from a business perspective, is it really worth it to spend thousands of hours and thousands of dollars on development time if only a handful of people want to join? If the market cannot offset the cost, and it's a losing proposition, then it's not worth it.
I am only a moderator, not a Team member, so I really can't give you an accurate answer on when or if it will happen, but I would not plan on seeing anything in the 'near future'. (Usually there's some buzz about a new club ramping up but to date, I've heard nothing besides the quote I provided from Andy in my initial response.)
RT has a lot to offer, and phpBB3 is quite powerful, and in fact it's what we use here.
While you are waiting, you might want to give phpBB3 a test drive.
There might be one that would closely match whatever template you are using (if you are using Joomla as well).
And of course, searching or posting on the vBulliten forums might get you started in customizing your own theme or get you pointed in the right direction.