It seems EBU has set the date as September 15, 2015 for the various broadcasters to submit their application to take part in the Eurovision song contest 2016 in Stockholm next May. As usual, there also the safety date of October 10 to rethink and cancel the participation if one has economical difficulties etc. Any cancellation after that date will lead to financial sactions - at least in theory.
So far 25 countries have confirmed or shown interest to take part, among them Ukraine and Turkey.
Out of Big5 we are still waiting for Italy but then they usually let the confirmed countries list released by EBU do the talking and there's no need think why they wouldn't be present in Stockholm.
Albania, Cyprus, Macedonia, Poland, Portugal, San Marino and Slovenia are expected to confirm and take part while Bosnia & Herzegovina and Bulgaria might return, if they solve their financial problems. Croatia has hinted a return but then you never know.
Andorra, Luxembourg, Monaco and Morocco are not returning.