I don't know. I just saw this post and was curious
After the horrible treatment RRR gave to Pale Communion's promotion and releasing, Opeth signed to Nuclear Blast, under their own label, Moterbolaget Records.
While I don't really know what exactly happened with RR and Opeth in particular, I was able to find this on (not a great source, but still) Wikipedia:
On April 26, 2012, it was announced that Warner Music Group were to make substantial cutbacks throughout Roadrunner Records worldwide operations. According to staff working at the company, The UK offices and the Canadian offices of Roadrunner Records are to be closed completely, with severe levels of cutbacks occurring across the rest of the label worldwide. It has also been announced that the Roadrunner office in The Netherlands is to close, and that the label's founder Cees Wessels is stepping down from his role of CEO. The following years saw several major Roadrunner acts leave the label, including DevilDriver (who moved to Napalm Records), Opeth, Machine Head, Soulfly and Lamb of God (all of whom moved to Nuclear Blast).
My bet is that these european branches managed the Opeth deal and, once the cutbacks started to happen, they weren't giving them the treatment they expected/signed for.
I'm still curious to see if DT have one more album with RR or not. If they still have to make another album with RR, but want to go somewhere else, they can always release a "best of" album and that pretty much solves it. The previous compilation was only for the albums from IAW to OV, so they could fit some songs from SC to TA (or even just the last 3 albums) and put it out as a compilation.
After that, if they want to leave, I don't see them self releasing anything. They've always worked with labels and I don't think why DT would stop working with one. They're one of the few bands in the genere who can sign with pretty much any label out there.