Fight your way out; only scrubs and mashers jump out of the corner
A common approach they might use is to begin supporting their own login mechanism while also federating login to other services, like XBL or PSN.
I personally hope they use openid to manage identity and simply allow us to link PSN and XBL identities; that way everyone would have one less user name / password to remember and could sign in using any of a number of identity services ( facebook, twitter, linked in, myopenid, etc )