http://www.gateworld.net/news/2008/08/sci_fi_confirms_iatlantisi_cance.shtml
It will end this January with the final 100th episode and will have a 2hr movie to wrap up the story line similar to how SG1 ended.
There still is no word on the Stargate Universe series, but alteast there will be a movie and potentially more to follow. Guess, I'll be down to only 2 shows worth watching, Heroes and Dexter.