Really not sure they are going to get anywhere in court as the new rules just means it takes them slightly longer to get British Citizenship, and surely if they want British Citizenship it should mean they were planning to stay in the UK anyway. At best there might be some transitional arrangements for existing visa holders, but it won't help anyone newly coming into the country.
The only mistake the Government has made is not implementing tighter rules long ago. Some of the current rules are a bit silly to say the least - eg if someone can manage to stay here for 10 years on students visa they can obtain ILR.
You can read the proposed rules to see what the government is planning. In my opinion they might be tweaked slightly, but I can't see any major changes being done to them.