Most likely substitute for me is a combination of Facebook and self-hosted. Primary posting to self-hosted replicated to Facebook. 90% of LJ people on my friends list are already on Facebook. And since I more or less won't be doing private posts anymore it doesn't seem too important to utilize the friends-list exclusion features that aren't practical if I self-host.
Frankly, the only reason I keep the LJ as my primary location is inertia. Both my own and my friends'. I've had ten or so people ask what happened to my book posts, despite posting fairly frequently that I've moved them to Rat's Reading (ratreading). Few subscribe to blogs or even to the LJ feed of it. I'm not complaining though. Point being, that if I drop LJ practically speaking I'd lose most of my ability to inform/annoy my friends. And on my own end, I commit an economic error by not being willing to let go of my sunk cost in spending money on a permanent account. (I've recouped the cost though. I bought mine in like 2003.)
Though writing this all out makes me think I should consider an experiment. Start up the self-hosted thing, and then replicate directly in to LJ and Facebook (as in, not an LJ syndicated feed).
Hmmm... I'll put it on the list of projects I haven't