The reason has nothing to do with the banks and their rates.
Rates for "Jumbo Conforming" loans (loans over $417,000 that can be delivered to Fannie and Freddie) are higher because of LLPAs from Fannie and Freddie. LLPA stands for Loan Level Pricing Adjustment. It is an increase in the price charged to a bank to deliver a loan to Fannie or Freddie and is the basis used by the bank to determine the rate.
In this case, the Jumbo Conforming loans are subject to the Adverse Market Delivery Charge, all other applicable LLPAs, and the special LLPAs specific to Jumbo Comforming loans. Simply because of the unit loan volume, they are riskier to Fannie and Freddie and you will pay accordingly.
The American Housing Rescue and Foreclosure Prevention Act of 2008 raises conforming and government loan limits, but does not prohibit Fannie and Freddie from charging higher fees for these oversize loans.
It is extremely doubtful that waiting will save you money, considering that Fannie and Freddie have serious financial problems including a capital shortgage, loss on investor confidence, drop in the exchange value of the dollar (thus forcing Fannie/Freddie to promise higher nominal yields on MBSs to attract foreign investment) as well as increasing competition for investor dollars from foreign markets.
There is absolutely no financial or economic reason on the horizon why rates should drop as low as you hope especially on high risk (eg Jumbo Conforming) loans. You would be wise to lock what you are offered. If things improve as you hope you could refinance... refinancing early in a loan is much less costly than several years into a loan.
Please don't wait for a lower rate, and good luck to you.