Assuming you mean level 4 or 5: Impossible to know. We don't know how many surprises need to be resolved until anyone has done it. The possibility space is so

Assuming you mean level 4 or 5: Impossible to know. We don't know how many surprises need to be resolved until anyone has done it. The possibility space is so wide the company may go bankrupt before it gets there on the higher-difficulty estimates of timescales. On the short-timescale estimates, the only reason I'm confident Tesla don't already level 4 in an alpha version, is that Musk would've shown off an uncut 54 hour video of it crossing the USA from just south of the Canadian border by Vancouver to Key West in Florida if he'd been able to.