The USGA and the R&A just issued an Area of Interest Notice proposing that the Driver length shall be limited to 46" plus 1/2" allowance for grip.  This is in an attempt to avoid further increases in driving distance.  Tall people with short arms will need a special permit to play longer clubs.  Personally, I think this will complicate the rules further.  If it is not broken, why fix it?

Here is the letter from the USGA.