News at Ten has ended at the usual time, despite May being expected shortly. A little surprising given the importance of any announcement, but I suppose the argument for going off air is that May could be half an hour or even an hour later than expected.
Given how media conscious May’s team is, I suspect there is some annoyance from No. 10 that both main news bulletins have been missed.
May's announcements are generally empty and she's a PM who has repeatedly avoided the media, so no coincidence the announcement falls after the bulletin. The speech itself isn't the news anyway, it's the analysis and fall out which they're doing this morning anyway.
Ultimately though nothing has changed due to last nights announcement. Indeed nothing has changed since this deal was first due to be voted on three months ago.
May and her team seem to try to control the media rather than avoid it. Questions submitted in advance, limited interviews, etc.
When May made the announcement outside No. 10 (when BBC One was showing the football), she left it until slightly after 10pm so the news programs could start and show the speech in full. It would have been in May’s interest for the press conference to be shown on both bulletins, even if the deal hasn’t really changed.