Somewhere back in the cobwebs of my mind, I believe they are bringing out the updated book and the map this winter. However, even if they do not, using the current book and/or maps will get you 90% of any altered route and then you will only have to deal with the up to 10% change.
One thing to consider is to look at alternate routes. For instance, you are so close to Glacier National Park, it would be a shame not to ride Going to the Sun Highway, even if it is an up and back two day diversion. You could also start in Jasper and take in the Icefields Highway (great!). If you do not want to do the Great Basin, you could ride south from Jackson, WY to Kemmerer along Grays River Road/Little Fall Creek Rd. then a paved stretch to Rock Springs before beginning a deserted stretch of CR-4 in Colorado to Slater where you reconnect. The point is do some research on alternatives that YOU find interesting/enjoyable. The GDMBR will have plenty of research so you can make a decision as to what route YOU want to take in 2015.
Whatever you do, enjoy the ride!