Decommissioning Marketo

"it will be like it never existed", to paraphrase the "Delete Program" message. Not exactly sure what the background is of your question, but when Marketo shuts down an instance, it is not available anymore in any way: you can't login, landing pages and forms are offline, images & files cannot be reached anymore, etc. I believe a backup may be kept for a little while, but for all intents and purposes, consider it deleted.