We actually had this confirmed the other day, but I didn't put it up because I thought it was already obvious. Because people are still asking on the forums, yes: everyone (all classes) will be getting a free respec when the expansion releases, whether you choose to purchase the expansion or not.
Which is probably good news if you're planning to respec near the end of this year, and didn't want to spend the 5g. But as I said, with all the new talents coming out, rumored or otherwise, how could you not respec? It is pretty momentous that they're handing them out across the board-- I don't recall Blizzard ever having done that before. But considering how much they're changing everything, it's only the right thing to do.
A better question might be this: What will the world of Azeroth be like for the week after the expansion, when everyone comes back to find new and varied talents, and almost everyone has to L2P again? Will free respecs make us all noobs again, or will players be more than ready to jump in and use what they've been given like pros?