Nothing stops them from coming out with a more traditional truck later except that it clearly takes them many years to ship a new model, and all the while customers who want a truck now or don't want a cybertruck are going to competitors.
Of course at this point they are committed to release. But I agree with others that releasing a more traditional truck would have been more savvy.
I don't know much about their status but other people in this thread suggest their factory is tooled up and they are close to release, so it might be a bad time to cancel everything and go back to the drawing board. Then they would have no truck for another 5 years.
But Mr. Musk is playing 11th dimensional chess that the rest of us are incapable of understanding. But more seriously, there are reasons they didn't start on it until now, maybe those reasons will persist and they'll get past the sunk cost fallacy and just decide to cancel it.
Even then, what's the chance that Tesla will remember who gave them a $99 deposit. SpaceX completely forgot about how I gave them $599 for a downlink terminal. I had to email them scans of my credit card bills to convince them to look for their records of the transaction so they could refund the charge on my credit card. (And even then, they only refunded $500 or the $599 I spent.)
But I'm grousing about SpaceX, I'm sure Tesla has a better AR/AP/CS system.
Of course at this point they are committed to release. But I agree with others that releasing a more traditional truck would have been more savvy.