I doubt you'll get a definitive answer, at least at this time, because they probably haven't decided themselves yet.
From what we know, for at least a time, a vendor will exist where you can take these "tokens" that you have from items you bought in the store and trade them in. so you take an otterbear pup "token" to a pet vendor and trade it for the ingame otterbear pup
I believe it was said that they can run out of stock for a time. and it may even be possible to kill them.
MY guess is that items from the store will be available in expo and then at launch for one life-cycle (52 weeks) and then anything not redeemed will be turned into Story Points