Final answer:
Based on Erik Erikson's theory, the likely developmental stage outcome for a 20-month-old toddler is autonomy. The supportive approach taken by the mother in the scenario with toilet training is conducive to fostering this sense of independence.
Step-by-step explanation:
The likely outcome for a toddler's developmental stage, based on Erik Erikson's theory, is autonomy. During the toddler stage, which ranges from about 1-3 years of age, children are in what Erikson identifies as the autonomy versus shame and doubt stage. This stage is characterized by toddlers learning to exert their will and establish independence, which can be manifested through wanting to make small decisions for themselves, such as choosing clothes or initiating toilet training. The mother's supportive response, recognizing her son's current disinterest in toilet training and deciding to try again later, is likely to foster an environment where the child can achieve a positive sense of autonomy rather than developing feelings of shame and doubt.