It seems that the Set objShell line is not required as your objShell variable is never used and is redundant with oShell.
VBScripts will quit without the wscript.quit(ExitCode) call when the end of the file is reached, but if you're calling this from something else, the 1 exit code will allow you to know that the user said they did not want to reboot (the default exit code when the end of the file is reached without errors is 0).
I wouldn't have used a case statement - that's generally only used style-wise if you're selecting from a series of options. More likely I'd have coded the last section like this, but this doesn't change the functionality at all.
If retCode = 6 Or retCode = -1 Then
objShell.Run "elevaterestart.bat"
Else
WScript.quit(1)
End If