3. Author J.K. Rowling has moved on to other projects. Whilst she's recently penned the short story and has added bits and bobs to her Pottermore site, 48-year-old Rowling has moved on and has published a number of books not remotely related to the Wizarding World. 

JK Rowling
Author J.K. Rowling has published three adult fiction books since Harry Potter.

It's been seven years since the last Harry Potter book was finished and in that space of time she has penned three books including The Casual Vacancy, published under her own name in 2012 and, as it was revealed last year, two books under the pen name Robert Galbraith. The Cuckoo's Calling and The Silkworm have been hugely successful, especially since Galbraith's real identity was revealed.

4. The cast and crew have moved on. The last film, Harry Potter and the Deathly Hallows Part 2, was released in 2011 and since then many of the young actors have enjoyed varied careers. Daniel Radcliffe, who starred as Harry in the film series, has a varied and acclaimed stage career having played Equus in 2007 and a musical, How to Suceed in Business, in 2011. He has also starred in numerous films including The Woman in Black and Kill Your Darlings. 

Daniel Radcliffe
Danuel Radcliffe has since appeared in numerous stage productions, pictured above on the opening night of The Cripple of Inishmaan in New York.

Whilst Emma Watson, who played Hermione, has gone on to be an audience favourite and has appeared in such films as The Bling Ring and Noah. She has also enjoyed a modelling career and was recently appointed a UN Goodwill Ambassador. Rupert Grint, who starred as Ron, has been pushed slightly out of the limelight but is set to appear in an upcoming CBS pilot Super Clyde. The point being, the actors are on to other projects and whilst it may be financially attractive to appear in another Potter film, it may interfere with how they wish to be thought of, not simply as their Harry Potter characters. 

5. The actors are still too young to play their 34 year old selves as the new story needs. Whilst the actors were aged using special effects for the last scene of Harry Potter and the Deathly Hallows Part 2, it was only for a small section of the film and would be highly impractical to have a whole group of actors aged when they are in their early twenties. Radcliffe, as the Irish Independent reports, mentioned this issue and explained as one of the reasons that Harry's "12 years older than I am now."

Read More: Fantastic Beasts And Where To Find Them Will Be Filmed In The UK.

Emma Watson
Emma Watson, who starred as Hermione Granger, recently starred in Noah.