Doctor Who>>> Is David Tennant coming back? Also, is Rose?

I like David Tennant. I thought he was the best doctor. Is he coming back? I think in the last season four episode we got rid of Donna, but the Doctor was still the same. Is he staying for the full fifth season? Also, I REALLY liked Rose Tyler. She has been my favorite companion and i was sad when she left and then when they made her leave again. Is she gone forever or...? Last, when does the next season start? Or has it already? Season five. Thanks! Also, give your opinions on David and Billie (The doctor-David Tennant, Rose- Billie Piper) Thanks!