I think we can count out the idea of an SG-1 feature film anytime soon. Since Dean Devlin has recently struck a deal with MGM about producing the sequel films to Stargate (which will pretend that SG-1 never happened and be totally out of the TV series' continuity), there is little chance that MGM will also produce a competing SG-1 film and "confuse" the movie-goers.
Conspiracy theories anyone? I find it odd that Devlin makes his announcement, and SG-1 is cancelled a month later. Theatrical releases are where the big money is. A sure way to whet the fans' appetites would be to cancel the series, leaving them hungry and dying to see anything SG...even an SG movie that has nothing to do with the beloved series.