Whether a board member could sue for wrongful dismissal or not is moot. Anybody can sue, it's whether they have a case that would prevail. In THIS case, it's pretty easy to read between the lines and conclude that the board members each received some sort of package (eg: paid out until the end of their board term, or something like that). Why do I conclude this? By the complete lack of comment from any of the board members. This implies that they have received a package and signed an NDA. You see, it's not often that "wrongful dismissal" cases end up in court - the majority are settled well before it gets to that stage. And for Ford, silence on this is golden (worth the cost). Remember, his reasoning for firing the CEO and the board was strictly because of compensation - which is really missing the forest for the trees and stupid reasoning when he could have raised other potentially legitimate issues after assuming power. But these days, pandering to the lowest common denominator has never hurt.
Now pay attention to the details of who Ford chooses to fill the vacancies, in particular how compensation is spelled out. Unless he's planning on hiring his nephew, Mike Harris Jr, David Price, or some know nothing hack like Kory Teneycke, he won't get get any competent leaders at significantly less than he just let go.