I don't know how reliable the source is, but from Three Guys and a Podcast (as seen on Slashgear):
Since Apple has quit attending the MacWorld trade show, MacBook Pro launches roughly follow a fall or spring release schedule. This year proved to be different due to the MacBook air being the major Mac focus for the fall/winter timeframe. January will likely be reserved for Apple's annual iPad refresh. This leaves April as Apple's launching point for the all-new MacBook Pro design. We don't believe this will be a simple refresh of the MacBook Pro, rather, Apple will deliver an all-out redesign, the big brother of the MacBook air.
April is also when the annual NAB trade show takes place, which has pro users scouring the market for new solutions. Couple this with Steve Jobs recent email response of "buckle up" regarding a Final Cut Pro update and an April launch mates perfectly with the perfect audience.
The iPhone launch revealed the design direction of the next generation iPod (which became the iPod touch). The new MacBook air shows us exactly where Apple is going with the MacBook Pro line of product.
The new MacBook Pros will move to solid state storage, up to 512GB, remove the optical drive, and we believe light-peak is being pushed to make it's first-ever entrance into the market, another Apple exclusive.
In the same manner that the MacBook air did not replace the traditional 13" MacBook Pro, Apple is likely to leave one legacy 15" design in the lineup for those not yet comfortable with Apple's new direction. The traditional model is likely to slot into the $1,799 position with upgrade options available, while the new MacBook Pros will start at $1,999 and scale up according to configuration.