If, in some unlikely hypothetical, they canceled the season, the league wouldn't use the same draft order as the previous year.
They would create a "draft lottery" televised event they could sell to the highest bidder to generate extra money for themselves. Hockey and basketball's lotteries are decent events, but if the NFL did it (and did it after being away for a whole season so fans were starving for football content), it would be a monster TV ratings event worth a lot of money.
But the league won't cancel the season unless they're forced to. They'll play without crowds and give up the concession/parking/ticket money before they cancel altogether.
And if they get a late start, they'll just play a shortened schedule (say, a 10-game schedule where each team plays their normal 6 home-and-aways with their own division and then also plays one other division for an addition 4 games to fill out the schedule). Make no mistake, the league thinks the show must go on. There's too much money to make by putting their product on TV this season. Especially if the TV landscape is hindered with interruptions to TV productions, leaving the NFL to be an even bigger ratings monster than usual because they're the only game in town.