I have just bought it as a present for my son and thus am keeping it sealed for now. I am wondering if it is likely that it will have all the balance changes incorporated; has there been a printing with these changes? How about the additional faction sets? Thanks.
Do you know if you bought the 1st Printing or 2nd Printing? The latter should be most/all of what's available from distributors and includes all the latest balance changes (sans anything for Onslaught 3, which is still getting ready for production), but the former is probably still floating around individual and third-party sellers.
It won't include any of the additional faction sets, if that's what you're asking, but those should be available at various places online. The only expansion faction with errata changes that I'm aware of is Windwalker, so I believe you'd also be dealing with a 1st Printing vs 2nd Printing issue there, but IIRC Petersen Games' online store and Miniatures Market only have the 2nd Printing in stock, so you shouldn't have to worry.