I also think the Holmes brothers already have a very strong bond. (Just think of the morgue scene in "A Scandal". Mycroft Holmes lecturing his little brother on the advantages of not caring, and the moment Sherlock is out of the building he is on the phone with 221b to make sure Sherlock won't be alone when he gets there.)
They would be loath to admit how much they care though, and this is part of the beauty of their relationship, so I am not sure I would even want it to change that much.
But I would be very happy to learn a bit more about the Holmes brothers' background in series 3, and I think we will be getting just that.
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"When you walk with Sherlock Holmes, you see the battlefield" M.H.
"My brother has the brain of scientist or a philosopher, and yet he elects to be a detective...what might we deduce about his heart?" M.H.
"Home is now behind you, the world is ahead."