I think it will work out fine, but your biggest problems will be getting them to fall asleep and not bother each other, and the possibility of one waking the other up in the night or early morning. My brother's 2 year old triplets all share a room, and although they occasionally wake each other up in the night, on the whole they do pretty well. Our kids share a room and they never wake each other up (DS1 is a really deep sleeper) but they do have trouble falling asleep without getting too silly together. Our solution right now is for one parent to sit in there monitoring them until one of them falls asleep, and then the other is fine on his own. I love that they'll have memories of sharing a room-- I think that it's really great for siblings and helps them grow closer to one another.
Mommy to two boys, ages 4 and 6.