So, we are entering run-up season - we pretty much know it'll start in the same week as last year (week beginning 12th October).
I absolutely love the run up to the show, and I have done some research/guesswork about when trailers, exclusives, and the candidate reveal will take place, based on Series 9 and 10.
Series 9
Fri 12th April: First trailer ('Finger of Fear') [3 weeks, 4 days]
Fri 19th April: Teaser clip on the website with soundbites of the candidates [2 weeks, 4 days]
Tues 30th April: The candidate reveal [1 week]
Fri 3rd May: A second set of trailers released, showing the candidates talking about themselves [4 days]
Series 10
Sat 27th Sep: First trailer (repeat of Series 9's one) [2 weeks, 3 days]
Wed 1st - Sat 4th Oct: Candidate 'teasers' posted on Twitter and website [1 week, 6 days - 1 week, 3 days]
Tues 7th Oct: Candidate reveal [1 week] AND trailer featuring the clips from the series [1 week]
Seeing as Series 11 is airing at the same time as Series 10, so I think Series 10 is more reliable as a guide.
Based on this I think we can expect a preliminary trailer next weekend, and the candidates to be revealed in about 2 and a half weeks. How exciting!