I think a vet FA and a draft pick are warranted this year. Henry is a little older and while I feel he is still a pretty good player having his replacement on the roster is a good idea. Plus, if a FA or rookie can step in and be an upgrade at the starting spot then that is all the better.
Also, I think Henry could still be shifted to free safety. He played S in college and early on some in Cleveland. If Hamlin leaves or if Roy were to be traded, released, or benched. That move may be needed.
Lastly, sometimes rookie corners take some time to develop and adjust to the NFL. Especially, a guy like McKelvin (whom I like) will have to adjust to a big jump in competition. You would hate to lose some games early because a rookie is starting or in the all important 3rd corner role before they are ready. A guy like Drayton Florence would be nice. I watched his play against Welker as well and I think he did a pretty good job. The ties to Wade will be a plus. In today's NFL a teeam really needs 3 corners who can start and 4 is even better.