I know a lot of people are excited by the prospect of releasing on 360 eventually. Looks like things are going to get even tougher even after you put up the $100k to develop a title. I Imagine 6%+ conversion rates are hard to keep indefinately.
http://www.next-gen.biz/index.php?option=com_content&task=view&id=10620&Itemid=2
XBLA titles that have been out for more than six months, have a Metacritic score of less than 65%, and have a conversion rate of less than 6% will be eligible for desliting. Microsoft will give three months of notice before these titles are removed.
http://www.next-gen.biz/index.php?option=com_content&task=view&id=10620&Itemid=2