It's been a while since I've looked into the HD market as I bought two TC's for backup and really haven't used my external drive enclosure or thought much about it. I looked up prices today and was shocked that they are up to 6TB drives with 4TB drives being affordable. Talk about living under a rock. Where have I been? They must be planning a refresh soon. But....
Why not get a refurbished TC now. They are the best deal on the refurbished store and are future proof in the sense that they won't get cheaper when a refresh does occur. If you have a reason you could use more than 3TB, you might wait.