i was just wonering because i'm gonna get the msi r9 280 gaming edition graphics card but i was wondering if i could get something like a r9 270x down the line?
Nope. You'd have to get another 280
a 280x would also work, but it would perform like 2 280s.
A 280 is about equivalent to a 7950 Boost Edition, and a 280x is a 7970 GHz Edition, so yes you could technically do it, although there'd really be no point to that, since you're spending extra money on a 280x.
OP, you could also get a 7950