I'm filing this one squarely in the rumor category but a source at 9-to-5 Mac claims that Apple is planning "minor" updates to MacBooks and MacBook Pros at WWDC which runs from June 8-12 in San Francisco.
He said he wasn't sure what the minor upgrade was but there was speculation that there might be some sort of 3G hardware built-in and/or speed bumps. Perhaps even non-removable batteries on the smaller sized laptops. Again, that part is just speculation at this time.
The story was updated today (via The Register) saying that the MacBook Pro could get an OLED option:
An LG staffer has made the very bold claim that 15in Apple notebooks equipped with OLED displays will appear within months... the mole added that once Apple’s unveiled its 15in OLED notebook, LG will then launch its own standalone 15in OLED panels later in the year.
The 9-to-5 source also said to expect a "big" Pro apps update which we could assume will include Final Cut Pro, Aperture, Logic and Shake.