From the Riverside Facebook page:
Dear Friends,
We’d like to thank you again for your friendship and support throughout this most tragic time for us and we’d like to officially announce that we have made a decision about our future.
We have decided that we are not going to do a casting for a new guitarist. Thus we have ceased to be a quartet and have become a trio. In this line-up we will prepare our new studio album. Both in the recording studio and on tour – if we get back to touring – we will be playing with session guitarists, who are our friends, whom we know and like. But the line-up of Riverside will be as shown in the picture.
Yes, we do realise that this is not going to be the same band. We know that for many of you the story of Riverside ends here, this year, and that “Eye of the Soundscape” might be the last Riverside album you’ll buy. We know that some of you can’t imagine this band without the characteristic guitar of Piotr Grudziński and for you Riverside has ceased to exist. But our story is not over yet; with a flaw, with a scar, with a wealth of new experiences, we have decided to go on.
The boys in black have embarked on their final tour, and I was fortunate enough to see them perform at the MGM Grand Garden Arena last night. Geezer, Tony, and Ozzy (still missing Bill Ward!) played all the hits (“Black Sabbath”, “Snowblind”, “Iron Man”, “War Pigs”, etc.) before ending the night with the classic “Paranoid.” The original members were not the only standouts, however: young drummer Tommy Clufetos rocked as hard and played as well as Geezer and Tony. His lengthy and frenetic drum solo about halfway through the show was certainly a highlight.
It’s unavoidable. It is impossible to speak of modern music, regardless of genre, and not take note of the critical importance of Miles Davis. Call him what you will or what he called himself — a genius of composition, a dazzling trumpeter/performer and band leader/manipulator, an agent provocateur, a counter-racist, coke fiend, pimp, misogynist — Miles Davis was to musical art what Pablo Picasso was to visual art in the 20th century. It’s so true it’s not even up for debate, and there’s about a kazillion hours of recorded, generous, lovely, dark, funky, bopping proof. By natural extension Davis was the incarnation of what 
Progarchy 