"[the loss of the deductions for State and Local taxes is] going to mean a middle class tax increase of such substantial proportion that it won't be offset by the larger exemption offered"

That's possible, but there isn't yet nearly enough information to say it definitively. Two big pieces of information we need are:

1) Where will the 25% tax rate start? If it's up near the current 25% levels (e.g. $75,900 for married filing jointly), then people near the middles of the current 15% brackets may well see a tax decrease. If it's down near the current 15% threshold ($18,650 for MFJ), then many in the current 15% brackets will likely see a tax increase.

2) Child Tax Credit (currently $1000 per kid). If it increases significantly (say, to $2000 per kid), people with 2 or more kids will likely see a net tax decrease.

Of course, there's also the fact that losing the state/local tax deduction only affects those who itemize - which only about 1/3 of filers actually do.