This from the RSC's website:

Latest news at 5 Jan: David Tennant has made good progress following his recent back operation and will perform the title role in Hamlet this evening. Edward Bennett returns to his original role as Laertes, along with Tom Davey, Ricky Champ and Robert Curtis who will play Guildenstern, Lucianus, and Francisco.

We will be assessing David's return to each Hamlet performance this week on a day by day basis.

Hamlet plays at the Novello Theatre in London from 3 December 2008 - 10 January 2009 after transferring from Stratford-upon-Avon.

Here's some reviews concerning Tennant's understudy--whom I belive we may hear more of in the future-- and the production in general:

'It says much for the quality of Greg Doran's production and the depth of the RSC ensemble that David Tennant’s understudy, Edward Bennett, assumed the role with great style and achieved a well-deserved ovation at the curtain call. Much of the strength of Doran's production lies in the surrounding casting. Patrick Stewart is a masterly Claudius, who starts as a smoothly duplicitous figure, slowly disintegrating. By the end he is so aware he has been outwitted that he almost gratefully accepts the poisoned cup from Hamlet. And when was there a better Polonius than Oliver Ford Davies? He has exactly the right mix of courtly sycophancy, personal cunning and sad senility. This is a first rate production that gives Edward Bennett a well-merited moment in the sun.' --Guardian

'It is a bold, fast-paced production, and beautifully acted production. It is hard to judge whether Patrick Stewart is better as the ghost or the king, both of them are so good. Penny Downie is a beautiful, elegant and thoroughly believable Gertrude. With such a rich cast and a director at the top of his form, even the absence of David Tennant cannot detract from a production which should be rated among the best modern Hamlets.' --Independent

Tho' I know they'll never see this, nor shall I ever see them, I do wish Mr. Tennant, Mr. Bennett and the rest of the cast-and crew, my heartfelt congradulations for what seems to be a top-notch production. Well done!