No, two surrounds plus the Beam is all you can have - other than the sub. You could swap the Fives for the Ones but that would be a bit overkill for surround effects, imho. 

You should consider adding a Sub to complete the 5.1 system.

Thanks for your help,
It's a shame because even though I have everything connected to TV, my true passion is listening to music and I think that configuration could have been very good.
I'll wait to see what happens and if SONOS decides to enable the option of four + BEAM speakers.
Thanks again.

If you primarily listen to music, you can add a pair of Fives in the same room and group them with your Beam and Ones just to play music.

Thanks, 

In case of grouping four speakers + BEAM in the same room, could I also listen to the TV without problems of latency in the sound?

No, there would be a delay to the Fives which would create a horrible echo effect. Streamed music would be in sync though. 

If music is your passion I would use just the Fives as a stereo pair set up to suit your listening position. I wouldn’t use them with the Beam/Ones as well: I think they will confuse and compromise the sound quality of just the Fives on their own. 

I agree with @nik9669a. IMO, the Five has always been Sonos’ best sounding speaker for music. I think you will be very pleased with two Fives set up as a stereo pair.