A slightly dirty Powershell module which includes a function for converting the results of the command-line Query User in to a Powershell object and a function for logging off disconnected users (with -whatif and -confirm).

RDPUser.psm1

# Example usage:
# Get-RDPUser | Disconnect-RDPUser -WhatIf

Function Get-RDPUser {
    [CmdletBinding()]
    Param()

    query user | Select -Skip 1 | ForEach-Object {
        
        $_ = $_ -split "\s\s+"
        $Username = ($_[0].trim(" ")).trim(">")

        If ($_[1] -match '^\d+$'){
            $SessionName = ''
            $ID = $_[1]
            $State = $_[2]
            $IdleTime = $_[3]
            $LogonDate = $_[4]
        }Else{
            $SessionName = $_[1]
            $ID = $_[2]
            $State = $_[3]
            $IdleTime = $_[4]
            $LogonDate = $_[5]
        }
        
        $Result = [ordered]@{
            Username = $Username
            SessionName = $SessionName
            ID = [Int]$ID
            State = $State
            IdleTime = $IdleTime
            LogonDate = [DateTime]::Parse($LogonDate,([Globalization.CultureInfo]::CreateSpecificCulture("$((get-culture).name)")))
        }
        New-Object PSObject -Property $Result    
    }

}

Function Disconnect-RDPUser {
    [CmdletBinding(SupportsShouldProcess = $true,ConfirmImpact='High')]
    Param(
        [Parameter(ValueFromPipelineByPropertyName=$True)]$ID,
        [Parameter(ValueFromPipelineByPropertyName=$True)]$Username,
        $State = "Disc"
    )
    
    $Logoff = $Input | Sort LogonDate | Where {$_.State -eq $State}
    $Count = ($Logoff).count
    $i = 0
    
    $Logoff | FT
    Write-Warning "Logging off $Count users"
    
    $Logoff | ForEach-Object {
        
        If ($PSCmdlet.ShouldProcess("$($_.username)","Log off"))
        {
            $i ++
            Write-Progress -Activity "Logging off $($_.username) from $Env:Computername" -Status "$i of $Count" -PercentComplete (($i/$Count)*100)
            Logoff $_.ID
        }
    }
}