谓语部分可能是1.we went on to have a discussion,是用以描述过去已发生的事;2.we would go on to have a discussion用以描述过去将来,即接着做;3.we will/are going to/are to have a discussion描述即将做;唯独不能说go on to have a discussion因为这种说法完全没有时态概念.
have a discussion中的discussion是可数名词,意思是1.(一次性的)讨论(活动);2.讨论会.