Somehow Roland Emmerich's perfectly mediocre Stargate inspired decades worth of perfectly mediocre TV shows, keeping that property sort of alive in a 'ripping off various iterations of Star Trek/Battlestar Galactica' way. I never expected to get Stargate back on the big screen because - well, because who cares? The basic premise of alien wormhole machines is so generic you could just steal it (ahem, sorry, homage it) and nobody would give a crap. It isn't like the extra-boring Erich von Däniken Chariots of the Gods stuff is very fresh or new anymore. Hell, I'd rather make a crazy Chariots of the Gods movie because that's a cooler title than Stargate.
But MGM got that Stargate IP and they gotta do something with it, and that something is a trilogy reboot. Of course a trilogy. I'm actually shocked they're not doing a series of unrelated films that can connect together in the team-up Stargate movie, actually. But they're not being that ambitious, they're just doing a new trilogy, and they have director Roland Emmerich and Dean Devlin back for it.
I think it's a reboot? I have no idea what any Hollywood buzzwords mean anymore; I know what remake means, and I know reboot should mean, but this is a 'reimagining?' What does that even realistically mean? Greg Silverman of Warner Bros (who is co-producing with MGM) says '[T]hese new films will build upon the creativity and popularity of the first film, while delivering an original film-going experience for fans and those new to the franchise,' which I think is also basically meaningless.
My guess? If they can get Kurt Russell back they'll make it a sequel to the original film, ignoring all the TV shows. If they can't they'll just remake the first film. Nobody will really notice the difference.
What's going to be interesting is seeing what the Stargate fan community looks like - their shows will be wiped from continuity, if I had to guess, and they'll probably be mad. This was already a marginal community - sort of like Farscape fans, except even more boring - so they should react quite negatively.