Yes it is possible to extract the wsp from the CA using the Power shell command.
Please take a look at this
To take single wsp backup use this
$farm = Get-SPFarm
$file = $farm.Solutions.Item(“JDSU.OneStop.wsp”).SolutionFile
$file.SaveAs(“c:\temp\JDSU.OneStop.wsp”)
To take multiple wsp backup use this powershell command
Start-Transcript "c:\wsp\transcript.txt"
[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SharePoint")
$solutions = [Microsoft.SharePoint.Administration.SPFarm]::Local.Solutions;
foreach ($solution in $solutions) {
$solution.SolutionFile.SaveAs("c:\wsp\" + $solution.Name);
}
Stop-Transcript
Hope this helps