Tease; Something Big Landing Tomorrow

Nokia Conversations have given us a teaser suggesting something big is arriving tomorrow (Tuesday 23rd July) with only the above picture as a clue.
They urge us to “tune in tomorrow 9am UK time” (Link Here) to find out what it is.
Going by the use of the word “big” it could be the 4.7 inch screened Lumia 625 which has been rumoured.
Anyone else have any guesses?