SIGMA is bringing another super-telephoto zoom to their lineup. This new lens will be a 150-600mm F5-6.3 DG DN OS | Sports, which appears to be for the mirrorless mount(s), so it could be for Sony's E-mount, SIGMA's L mount, and Nikon's Z mount.
I don't think this will be SIGMA's first RF mount release, so don't get your hopes up.
No specifications or pricing for the new lens have been released.
DG DN lenses are only available in Leica L and Sony E mounts.
Yeah, the costs of these RF lenses is aggravating. I can afford Sigma glass, but not Canon. As much as I love my R6, I'm considering jumping ship to Sony. I don't like their camera bodies, but I care about lenses more and Sigma has the affordable ones.
If we started seeing the Sigma DG DN series lenses and other third party lenses in RF mount, I might consider staying with Canon. Otherwise, Sony looks just so tempting because of the lenses available for the Sony system.