Lando sacrificing himself, I believe, would be superfluous. As Bingowings already mentioned, his redemption was putting himself on the line for months in order to save Han from Jabba. He was hanging around as a mole waiting to sabotage in one of the murkiest locations in the galaxy.

Only Han dying in the carbonite, which he obviously survived, would warrant Lando sacrificing himself at the Battle of Endor. I doubt Lando has much guilt left in his mind now that Han is rescued in no small part thanks to him.

That's why I vote that if we are going to have any of the heroes die in the final clash between Rebellion and Empire, it is better to have it be Han. To have rescued the rogue-turned-hero only to have him die soon afterward would add an extra sense of tragedy to the death.

In essence, they would have undertook a long, dangerous rescue mission just to have a few more precious days with their dear friend.

It's poetic.