Not really... That A specifies the gain of input pair alone! So you might have a dc gain of 1000.. But it might be due to a cascode or 2 stage or wat ever topology u select!
But question is about input capacitance! For that you must consider the Cgs and Cgd.. Since Cgd is affected by miller effect, you must consider the gain of the input pair also! I mean gm1 * R1, where R1 specifies the resistance of the input pair! Its better to keep the gain of input pair less to avoid larger parasitic cap at the input! Say if the gain is some 15 or 20, you have Cgs + 20 * Cgd!
Hope this helps!