The weight minimums are different for 2 and 4 strokes with the 2T getting the advantage. They will apply but the manufacturers won't make a machine lighter than the minimum. Too bad because I remember the 168 lb Pro Fab Husqvarna 125 that won the St. Louis Supercross many years ago. Titanium is a wonderful material!
The thing is, this trend is just at the local level. Imagine if Florida, Maryland, Colorado, and South Dakota did the same thing (actually it would be AMA Districts, not States). This really has no bearing on the US National (pro) Championship or the World Championship and might be a detriment to riders from these countries wanting to compete at the highest levels. Both Championships run under modified rules created by their organizers(i.e. MXsports (MX), Feld (SX) and Youthstream (FIM) . The AMA and FIM have pretty much rolled over and do whatever they (the organizers) want.
The only way this will have any effect is if a) the USA adopts it or b) if the EU (read FIM) adopts it across the board. The buying power of America or a combined EU would influence the manufacturers.