There really are essentially 5 WC positions available, and only a few weeks until the final decisions need to be made. As of right now you would have to assume:
James is a definite lock.
Donald, being in the top 100, and having the best results of the veterans, should be close to being assured a spot.
Smyczek has shown real improvement on the challenger tour and has earned a spot.
Personally, since Ryan has gotten WCs several times now, I'm not 100% he'll get another one. At this point, the fact Ryan has still not reached the top 100 has to be seen as a major failure. His ranking hasn't improved much from last year, and he defends a major amount of his points starting around now, so that means he hasn't made that jump up he needs. His ATP record this season is 2-7. He's 23 years old now and has been around the top 200 for 3-4 years, so he's on the bubble IMO.
Levine, Kendrick, Ram, Witten do not deserve spots. Not enough good results on the season. Maybe Jesse W. will get a WC due to him defending 3rd round points and his peaking at slams. If Jesse L. can show a little better these next few weeks to show that the Lexington final isn't a fluke, he may eke out a spot.
The final one/two WC positions will probably go to two young American hopefuls, like Harrison, Johnson and Klahn. Either Ryan S. will get one and then one young guy, or there will be 2 young guys, with either Smyczek or Sweeting out.
Not the best time to leave out a last name considering Harrison
I'm pretty sure Tomic will get the TennisAustralia wild card given his US Open juniors win last year.