Plant a Tree NOW? Yes, Now.
If your spade still pierces the ground, then you can still plant a tree. Trees go dormant during the winter months, so their roots systems are technically asleep. Planting them now is a great idea!
Dig a hole now while the ground is still easy to penetrate and store your soil in a wheel barrel in the garage. Once your tree is shipped, plant it and use the soil you stored. Be sure to top the tree with mulch and water like you would in the spring/summer to lock in moisture.
So when spring rolls around your tree will be settled and ready to burst into growth!