That is the exact size my dd was when she was born. (1#15.5 oz). My dd is now 7.
She pretty much followed her age curve with sizes. When she was 2, she wore a size 2, when she was 4, she wore a size 4. Now she's 7 and a size 7.
Just an FYI for some of the other posters, the SIZE of a infant at birth does not indicate how well s/he will "do". It is the numbers of weeks early. My dd was born 11 weeks early (at 29 wks). At 29 weeks, babies have a 95% rate of having no lasting effects of their premature birth.
I think clothes for next summer will make a great gift!

You can buy lots of cute t-shirts & socks. If you buy pants, make sure they have the adjustable waist, not just the elastic. My dd is very skinny and must wear slims or adjustable waist pants. Elastic bands do not work for her. With the t-shirts, if you don't quite "time" the size right, the Mom can always put a light sweater over the top. Hats, hats, hats are very important for preemies. When they are young, they need them to help keep the heat in and when they are older, to shade them from the sun. You can also include a gift receipt. Some stores (like Gymboree) will accept a return/exchange for up to six months. That way, if your sizing is "off" (cause we all know babies grow at their own pace), the Mom can exchange them several months from now.
Congrats to the new Mom & Dad!