Twitter is still planned for this year, but it likely won't be until later in the year. Development has begun, but it's going to be a bit more complex than we originally scoped due to substantial differences in their APIs from both Facebook or LinkedIn. Not insurmountable, but likely means we won't have a version out until around November.
The plan is to begin a Google+ extension directly after Twitter is released, but I can't really give a better timeline than first half of next year for when that would be available.
Hope that helps explain. Obviously, with development, anything can change.. so I don't want you to lock any decisions for your site or plans around the timeline above. We hope to hit those as they'd be great for us and our users, but as you've seen in other posts, we've been optimistic on our timelines before.
If you have any other questions, just let us know, and good luck!
Alex
Login / Register with Twitter and Google+
(time frame prone to slippage lol) 
