"Optimistic assumptions" refers to having positive expectations or beliefs about a certain situation or outcome. It means that one is thinking positively and hoping for the best possible result. Full definition
The comptroller says the budget is based on overly optimistic assumptions about revenues the city is counting on. (buffalonews.com)
Not only were the previous withdrawal rates based on overly optimistic assumptions for portfolio returns in today's low interest - rate world. (moneysense.ca)
Even under optimistic assumptions about timing and baseline scenarios, it's clear that little if any large - scale production of biofuels or biomass anywhere in the world even approaches carbon - neutrality. (carbontax.org)