Notably, Lattice manufactures the only FPGA for which a full open source design flow currently exists (albeit unsupported by Lattice themselves) , and has its own set of open source soft processor cores  .
So i don't see this sector changing with an open-source core.
If so , it will probably come from china - they're building all the parts, are hungry(even at the state level) to achieve dominance , and don't care much about legacies, and have the market (probably backed by government) to support such strategy.
Lattice on the other hand, is a more general purpose chip maker, so they may not want to bite the hand that feeds them. They've got a lot of products other than FPGAs, so keeping those lines working is probably more strategic than anything else.