http://www.scifi.com/atlantis/
It's a companion series not a replacement and SG-1 Cast will be making the occasional crossover into the show.
It says the adventures take place AFTER the SG-1 series and refers to jack O'niel as General O'niel so it sounds like this will take place a little into our future.
http://www.gateworld.net/atlantis/s1/101.shtml only one guy looks like he's in modern uniform two of them
"SPOILERS POSSIBLE!"
I KNOW are aliens so they are wearing their own uniforms probobly and the one guy is just wearing an odd uniform so I dunno.
"SPOILER POSSIBLY"
They have a new enemy called the Wraiths I WANNA KNOW WHAT UP with the Goua'Ould?! They better not just leave the Goua'ould as a cliffhanger ending or some such because that would just piss me off
.