Two quotes from an interview about ME3 have done the rounds on the net this week:
"Obviously I can't say anything, but it wouldn't be a bad idea..."
Given ME3 is supposed to be the ending of a trilogy, the suggestion to keep one's saved games strongly hints that there will be a further Mass Effect game (4!?) which ties in directly to the events of the past three games. No surprise really as the Mass Effect series is a big seller and the cash cow needs to be milked. Not that I'm complaining, all the teaser reviews and the like are suggesting ME3 will be awesome.
