It has been a BJP tsunami in Uttar Pradesh. It is certain that the BJP is forming the government in Uttar Pradesh as it heads for a resounding victory in the state. There are a couple of factors that BJP would bear in mind before chosing a CM candidate. The social composition of castes who voted for the BJP would be one major factor.
The BJP would also keep in mind that it would require a very good performance in order to win the 2019 elections. The entire election in UP this year has worked on the non-Yadav OBC and upper caste mobilisation. Hence the party would need to choose a candidate who can keep both happy.