I wouldn't discount the possibility of a transaction tax. Democrats never met a tax they didn't like, and Republicans have proved they don't give a shit about ordianry investors and traders. The big wall street firms and mutual funds despise daytraders. They still blame us for spoiling the rigged game they had for years with 1/2 point spreads on nasdaq stocks and you couldn't post a limit bid. I can see a lot of votes for a fee to punish "irresponsible speculators". Of course, MMs and fiduciaries will be exempt.
Let's hope they don't aplly it to futures and options, but givne the hysteria when oil prices ran up earlier this year, they may just ban those markets altogether.