I think the idea is that MAN has the new bussing 'pier' ready early to give a lot of stand capacity whilst the others are being built (presumably, one by one).
I don't believe there is a T1/T3 detailed plan as yet. The industry evolves too quickly to need a plan for it all. At the moment, the plan is to get as many airlines as possible into T2 and then look to see what is needed in more detail in 10-15 years time I would have thought.