nVidia is not content to rest on their successes. While they've seen amazing success the past few years, ATI may turn the tables on them with their introduction 80nm process cards in the coming weeks. nVidia wants to beat them there, or at least get there much sooner than initially expected, and as such as ramped up their production schedule.
They will be trying to release updated versions of the G72 and G73 as soon as possible, and then release the highly hyped and anticipated G80. While I doubt hitting 80nm first will make a big impact on either vendor's lineup, it'll do them a lot of good in terms of marketing value. Considering ATI already committed to using 80nm over a year ago and is expected to release the first of these cards this month, it'll be a tough battle for nVidia.