Very good questions tier1extn1.
Unfortunately, I can't answer most of them but I was thinking myself about it.
Regarding how long consultation runs and how long changes will take.
If we look at Post-Study and Student changes, for me it was quite clear they are going to cancel Post-Study during summer 2010. They announced it recently but actual end of Post-Study will be April 2012. The same with student visa changes. So it took almost 2 years between initial declarations in political speeches until implemented rules. I hope it will take even more with Settlement because it's more serious area. However, nobody can be 100% sure it will be the same speed. But I don't think it can be much more faster.
Regarding your concern if it can affect your case. I don't know. I would say they absolutely MUST provide long transitional arrangements for people who already in the country. What they will actually do, god knows. From my own experience, they are not particularly nasty, nor humane. Expect something in the middle... they don't want to look too cruel but they also don't want to look too weak.
Correct me if I'm wrong.