As other fellows stated, GPWS is only using a major imput..the one from radio altimeter..and does not use any terrain databases...
the EGPWS, is a much more sofisticated stuff using different imputs, actual datas drom adc, and datas from a geographical databases..enabling the system to anticipate the flight path and trigger a warning in due time.
So a gpws does not need and is not fit to receive any update..and the egpws should be updated in due time..and this is normally proposed by the equipment manufacturer..Honneywell, Collins...etc..Sandel