Back in October of last year IBM announced that due to changes made by Yahoo, the Sametime Gatweway would lose support for Yahoo in January 2011. Today IBM announced a stay of execution for existing customers until mid-year:
“Hello Sametime users!
I am pleased to inform you that IBM has signed an agreement with Yahoo that will allow customers to extend the Sametime connection to Yahoo through mid 2011. This is for existing gateway customers, already connected. The replacement will be a Sametime Connect client plug in offering to connect to Yahoo using Yahoo IDs to authenticate. IBM will make this plugin available to existing and new customers. The exact release date this summer is not yet finalized, but our intent is to have this released before the Yahoo Gateway access is removed.
Please refer to the Lotus Sametime Support site for updates on this topic. “
So while Yahoo support is still going away, you have a bit longer. As for the replacement plugin, that will simply allow you to use your Sametime client to chat on Yahoo IM, but will require you to use a Yahoo ID and Password, this is similar to the AOL Chat integration that was in the Sametime 3.1 (I think that is the version) client.