I don't see the indications of SK market rapidly growing, in fact in terms of admissions, all three TF movies had very similar sales in SK. Perhaps the tickets got more expensive?
TF3 had one extraordinary opening in SK, but it was also much more frontloaded than previous films, and it's easy to see why: finale factor and the novelty of being the first TF film in 3D.
It's to early call TF4 a flop in SK, it may well be less frontloaded than TF3.