After last year’s absence, RTP promised Portugal would be back to compete in the Eurovision Song Contest 2017.
Their absence, they said, would also give them time to meditate on what changes to make to their selection methods as to get better results at the contest.
Now has become clear what those plans are:

There will be two semi-finals and a final, with the first semi-final being held on the 19th of February.
RTP has invited several, in Portugal very notable, contemporary composers:

Luísa Sobral
Márcia
Rita Redshoes
David Santos (Noiserv)
Celina da Piedade
Samuel Úria
Nuno Gonçalves (The Gift)
Pedro Silva Martins (Deolinda)
Tóli César Machado (GNR)
João Pedro Coimbra (Mesa)
Nuno Figueiredo (Virgem Suta)
Pedro Saraiva (Sir Aiva/D.R. Sax)
Nuno Feist 
Jorge Fernando 
João Só
Héber Marques

Almost all of them can be seen on this group picture (click the picture for a larger version):

Another revolutionary change is that the language rule has been dropped, the composers and/or artists are free to use whatever language they want.

The artists singing the songs will be announced in January.