I'm not sure if PP has announced this elsewhere, but Deborah Watling announced this week she is due to record the commentary for a DVD release of The Ice Warriors. I'm not sure if that means it will get it's missing episodes animated or not but there are rumours that another 3 stories are due to be animated (aside from 'Reign'), so it's likely I guess.
Great to hear. The Ice Warriors and The Tenth Planet are the only ones left with more than 50% surviving, so they'd presumably be chosen. The Crusade and The Moonbase would be possibilities too.