Define The Future

I work in the European Computer Services centre for a large multi national corp.
There is serious and open discussion around how IT services should be provided in the future. (We've been around a long time with plenty of legacy stuff to go with the new).

My question is simple enough.

Are there any models (systematic methodologies) that you can suggest to look at;
A) What we should look like
B) and how we get there

B I think is more important than A - we need to handle what I believe will amount to a sizable change management (and cultural change) process in a timely and effective way - while retaining our people.

I'm aware of SIS and OD, just looking to see what others have done. I'd like to learn from other people's experience.

Thanks