Pocket Gamer reports that Apple has decided to allow developers more room for their downloads; bringing the maximum size of iPhone and iPad apps from 2GB to 4GB.
Apple's site said this on the topic:
The size limit of an app package submitted through iTunes Connect has increased from 2 GB to 4 GB, so you can include more media in your submission and provide a more complete, rich user experience upon installation. Please keep in mind that this change does not affect the cellular network delivery size limit of 100 MB.
This is a huge deal, as games and apps can now have double the amount of content - but of course those with 16GB devices are going to fill their libraries a lot faster.