I think the average orbital height of the ISS is something like 350KM. The suit won't stay in orbit long without an external boost to overcome atmospheric drag. Maybe we can plot its eventual demise and watch for it burning up in the atmosphere.
I suppose you're right about how long it will be up there. Also, I suppose it will be interesting to some radio folk here on earth so it's not a total waste of time and/or resources.
With all the more legitimate research they could be doing, this just seems like such a bizarre thing to do: Hey, guys, I'm bored, let's toss some stuff out the hatch and see if anyone notices!
By the way, what are they supposed to be doing up there? (Unfortunately, that last comment is only half-sarcastic.)