Yes there will be a season 7, there are even a few spoilers roaming the internet about it. Desperate Housewives is locked in to an 8 سال contract (8 seasons). Though Marc چیری, آلو بالو the excecutive producer is trying to push it to 9 seasons یا even farther. Though so far it's on and it's not going anywhere. :)
there was an interview somewhere on fanpop where marc چیری, آلو بالو کہا he planned to end at season 7 something and now the producers want him to extend it