Anything wool (and particularly anything lace) should be able to block pretty hard. So yes, it will probably open up and get much wider/longer.

If I am am planning to do a hard block I usually note the before and after measurements on my Ravelry page.

Here is one: http://www.ravelry.com/projects/ashamanjababu/scarf-with-a-wide-and-handsome-border-for-a-mantel-drape-from-weldons-series-6-volume-2-1887

And another: http://www.ravelry.com/projects/ashamanjababu/peacock-tail-and-leaf-scarf

And you're a real knitter!