When both the weak acid solution and the naoh solution are diluted the curve will have less of a slope towards the end. What this means is that the titration is not as reactive and as diluted as much. The dilution will cause the concentration of the solutions to be more spread out and there will be a lot less of a reaction between the two. Another 10 times of dilution will make the slope even less reactive and will cause the reaction with naoh to be much less active than before.