Actually hold on, I think that there might be a problem with that.
This might happen…
Press W-walk and playfootstep=true
Additionally press S-walking diagonal and playfootstep=true
Release S-walking foward playfootsteps=False 
I think that will happen.
A quick fix (maybe not the best) is make variables for each key (playfootstepW, playfootstepS…) have each key set it’s respective variable to true and false. Then make each of those new variables all connect to the “condition” input in the branch.