Does an airplane going to new hires imply that anyone on the list could hold it?

For instance, 76 has been in new hire classes. Could I expect to hold it after my initial two year seat lock?

And extrapolating from that, with all things considered (retirements, pre-65 departures from the seniority list, growth) how many years do you guys think it will take to hold 75B and 330B?