Regeneration is not salvation... it is the quickening spoken of in Eph 2...
One is quickened so one can hear the gospel and repent and believe.
Regeneration___> Hearing_______>Repentance and Faith _______>salvation
That would make no sense.
When you are born you are born dead in Adam.
That is the basis of why were are spiritually dead, we are in Adam.
For as in Adam all die, so in Christ shall all be made alive (1Cor.15:22)
If you are regenerated you are now no longer spiritually dead and but, (according to Calvinism) not yet in Christ (which is where spiritual life is)
You are in a spiritual limbo, neither in Adam (dead/lost) nor in Christ (saved/alive)
You must be either one at any one moment, either spiritually dead or alive.
Salvation is not a process, it is an event, when you move from spiritual death (1st Adam) to spiritual life (2nd Adam) and that is through faith which precedes regeneration.