The way to increase demand for buying is simple: reduce price.
Changing the Power Down rules is an ex post facto action which economically harms those who have already Powered Up in reliance on the two-year period because it impairs the obligation of contract. As explained in the whitepaper, there are reasons for the two year period of reduced liquidity (a characterstic of the good bought) in exchange for greater influence on the platform.
Ironically, decreasing the Power Down time requirement also decreases the trust and confidence people have in Steem and the decision of whether to Power Up because the three month period can or likely will just be removed altogether as soon as it is beneficial to those who have the ability to do so.
So, why not wait until that happens? Thus, there will likely just be more potential investors sitting on the sidelines until Steem proves worthy of investment by being attractively priced and trustworthy in terms of the good they are buying.
RE: Steem Economic Changes Update