never works as a negative answer.- so you would rather respond
"neither will I" ... or "Nor will I"
... for the difference between  �neither � and  �nor � ... let �s have some native response ;o))
But, sure, you can �t use  �so �  ... you use "so will I" to confirm an affirmative statement:" I will continue to speak to him"   - "so will I."
... so sorry ;o)
But, "will"  ... will do well in both 1st and 2nd sentense ;o))