Joining numerous other companies who have opted out of large Expos in recent months, Nvidia has decided that Nvision is too expensive to host this year. Though they still plan to hold smaller conferences here and there, none will be on the scale that Nvision was last year.
If you recall, Nvision was used last year for several purposes ranging from demoing new technology to getting gamers involved with the company products and plans for its graphics products.
Several other technology conferences have been canceled as of recent, Intel skipped on some IDF meetings and Apple announced the very last Macworld Expo. The reasons may vary though they are all at least somewhat related to cost cutting given the current economic conditions. There is no mention from Nvidia if they will try to host Nvision next year.