It wont happen just imagine the amount of law suits they would end up facing from teams who got relegated or those who missed out on a european place it would cost them millions. But on a bright side for them they wouldnt have to worry about bilbao and barca booing the national anthem in copa final
Similar things happened in NBA and NHL, and the world survived.
About lawsuits, highly unlikely.
More or less any organization has an option in it's statute that in a case of unexpected events, they can arrange things differently than usual, according to an unexpected situation.
So, about lawsuits, I highly doubt that it would happen.
All clubs and all teams know that things like this can happen.
Still, I don't believe that there will be a strike, both sides are just trying to get into better positions with this threats.
But even if the la liga will be cancelled, nothing "spectacular" (imo), won't happen.
Some teams will slightly whine and that's it.