Not sure if the cost and the "lidar bump" will still be arguments in the future. Heck, the latest iPhone has a lidar sensor integrated! Surely with a lot less capabilities than what you would need in a car - but it proves that it can be built small and cheap. And I would say that more data from sensors that sense different things will always result in better decisions by autonomous driving software.
The gamble here is on the software, not the hardware. All the accidents that happen are not a failure of sensors not sensing but of software not detecting what the sensors captured. We're talking cars crashing into things on a clear day. Cars not recognizing situations that a human would recognize from the captured video. Etc. They need to solve that anyway. Regardless of whether they have lidar or not.
Other companies like Waymo pushing the Lidar agenda are also behind on their schedules to launch autonomous driving. But at least they have actual driver less cars on the road right now driving actual passengers around in very select markets.
Either way, this is more or less a greenfield market without a lot of contenders shipping actual products yet. So, Tesla can afford to spend more time developing this market. If they nail this somehow, eventually, it will be a big growth driver for them.