I think/hope it's an unstable equilibrium -- if either Altera/Intel or Xilinx/AMD give a nod to the open source tools, the others will follow.
Lattice is seemingly at "wink wink, nudge nudge" levels of support -- their lawyers won't allow them to say anything because they're afraid of pissing off Synopsys, but they also know that they're currently the best supported platform, and don't seem interested in deliberately making things difficult.
Lattice is seemingly at "wink wink, nudge nudge" levels of support -- their lawyers won't allow them to say anything because they're afraid of pissing off Synopsys, but they also know that they're currently the best supported platform, and don't seem interested in deliberately making things difficult.