Yes, Congress passed and the President signed a law that increases the loan amounts that can be purchased by Fannie and Freddie. The new "jumbo conforming" limits will vary according to location. The new limits will be up to 175% of the median home price in a given area, to a maximum of $729,750 (which is 175% of the regular conforming limit of $417,000). So, the $729,750 number that is often quoted may not necessarily apply to you if you live in a lower-priced area. And it's the government that determines what the median price and new limits are for the different geographical areas.
If you live in a high-cost area like the SF Bay area, then the new jumbo conforming limit is $729,750. This has already been declared by the government. If you live in an area where the median home price is $300,000, then the jumbo conforming limit will be $525,000.
Having said that, there's no guarantee that jumbo conforming loan rates are going to come down to the levels of the regular conforming loans. There are many analysts who think that it's not going to affect rates at all. The interest rates on mortgages do not follow lockstep with the Fed's actions, because the lenders have to take into account the long-term cost of lending. With the Fed's current trend of easing interest rates, this creates inflationary pressure. The lenders thus will want to protect themselves against inflation, and thus will not readily drop the 30-year fixed rate. In fact, inflation worries are more likely to increase mortgage rates, as has already been demonstrated since the Fed start easing last year.
Ironically, it's the ARM holders that stand to benefit the most from the Fed's actions. My ARM, for example, is tied to the 1-year LIBOR. I still have 5 years left of a fixed rate before my first adjustment. If it were to adjust today, my interest rate would drop to 4.5%, or nearly 2 percent lower than my fixed rate.