We report the constraints on the dark energy equation-of-state w(z) using the
latest 'Constitution' SNe sample combined with the WMAP5 and SDSS data. Based
on the localized principal component analysis and the model selection criteria,
we find that the LCDM model is generally consistent with the current data, yet
there exists weak hint of the possible dynamics of dark energy. In particular,
a model predicting w(z)-1 at z\in[0.5,0.75),
which means that w(z) crosses -1 in the range of z\in[0.25,0.75), is mildly
favored at 95% confidence level. Given the best fit model for current data as a
fiducial model, we make future forecast from the joint data sets of JDEM,
Planck and LSST, and we find that the future surveys can reduce the error bars
on the w bins by roughly a factor of 10 for a 5-w-bin model.Comment: Accepted by PRD; minor changes from v
