Nokia has sent out press invities announcing a new Lumia event scheduled for 14th of May.
The invite does not reveal much other than it is calling the press members to "see what's next" as "the Nokia Lumia story continues". The event is scheduled for May 14th in London, UK and with the recent leaks of the Lumia EOS and aluminum unibody it is quite likely that we might see the big Nokia comeback.
Since it is a Lumia event, it is also quite unlikely that we will see Nokia's push in the tablet market but according to previous leaks that will eventually happen as well.
In any case, be sure to mark the 14th of May as it might be quite an interesting announcement.