All will be resurrected, even the wicked. The plan of salvation existed and was planed before the foundation of this world. In general terms salvation is the inseparable connection of body and spirit so that the resurrected persons body lives forever. The levels of salvation mentioned are the symbolic levels of glory. The scriptures tell that in the resurrection their will be one glory of the star another glory of the moon and another of the Sun.
Salvation is the gift but progression and perfection are the process.
The PLAN of Salvation had been established before the arrival of Adam. An existing problem is that the doctrine of the pre existence of man has been ignored. For purposes of explanation only consider that Salvation may be at three levels. You will live forever just as you now live. You will live forever but will have the personal instruction of living prophets and very real promptings of the spirit.