Paul McGann, the short lived Eighth Doctor, was up until last November, the only (numbered) incarnation of the Doctor not to receive an on-screen regeneration - but in the thrilling minisode The Night of the Doctor, penned by Steven Moffat, the Eighth Doctor regenerated after seventeen years into the War Doctor, played by John Hurt.
Asked by a reader of Doctor Who Magazine if McGann will be returning for his own spin-off or a future episode, Moffat replied:
“We've been having a party. Every available and willing Doctor has been on that screen, one way or another, because it was a special time - even John Hurt showed up as a brand new mystery incarnation, and didn't he rock?”
“Paul McGann is a truly brilliant actor, and he totally gets the Doctor. I loved him, and I loved writing for him. It was an honour and a privilege to provide his final line (and how I paced, trying to think of it.) But it’s time for Doctor Who to get back to what it is, and always must be – one man, one TARDIS, the whole universe.”
“Remember those eyes in the The Day of the Doctor? The frowning brow, the stare? That stare is blazing at you from the future. The time of Capaldi is coming…”
[Source: Doctor Who TV]