OK, so our three cryptic pronouncements of this evening have been:
The Timeless Child
All will be seen
1558
Clearly, the Doctor got Elizabeth I pregnant back in The Day of the Doctor. That child will be the 'timeless child' because of some weird Time Lord biology thing (perhaps it ages much more slowly and appears to defy the passage of time). 'All Will Be Seen' is the title of a lost play by Shakespeare all about the Doctor and Elizabeth I and their child. In order to preserve history, the Doctor has to prevent Shakespeare from putting this play on. This will be the series finale and it will feature the return of the Zygons, the Carrionites and the Remnants (who will be revealed as the swaddling in which the timeless child was wrapped).
(c)