I'd list the job with the expected end date, and make clear in the description which hours are projected. You can also use the repeat function to have a date range beginning in May 2021 and ending whenever, which would clearly all be projected hours (other than what you might have completed in May). Either way, you'll receive whatever credit adcoms give to projected hours, which is apparently less than we would like! 🙂
You will also, of course, send an update letter later if things actually change. If everything else is ready, I wouldn't hold it just on account of maybe being more accurate on projected hours for a single activity.