I would make haste to attack on the queenside before your opponent attacks on the kingside, because your pawns are already pointing there and you have some good pawn break opportunities. 1.c4 bxc4 2.b5 axb5 3.Rxb5 and I wouldn't want to be in your opponent's shoes. In chess, fortune favors the bold.
Neutralised Queen-side
1.c4 Bg7 2.cxb5 axb5 and "white's attack sort of fizzles out" Black prepares for both ...Rxa5 and ...O-O
I think as long as White maintain the initiative... in other words, keeps pressing the queenside attack he wins no problem. 3.Ra1 O-O 4.a6 or 3.Ra1 Rxa5 bxa5 are both heavily in White's favor. If White can't decide where to attack, or plays passively, Black will eventually reorganize and strike back on the kingside.
Below is a position from a game I played recently as white. The way I looked at this position was to say "the queen-side is neutralised so lets go for the king-side". I'm not a very strong player and so my attempt to break open the king-side got me into trouble. Later when I went over this again I found that the queen-side attack was easier to pursue.
My question is, when you see this position, what is your reaction? Do you attack king-side because you see the space, or do you attack where the black pieces are most blocked up.
Apologies, if this is trivial. It's my first post and I'm new at this analysis thing.