I was rooting for the Boeing 2707 when I was a kid. Bigger, faster (Mach 2.7 vs Mach 2.02), no need for the nose to tip down. It was cancelled, probably wisely. This article said it needed to be made of titanium to work, and that was too expensive and the economy wasn't great. The Russian Tu-144 was a turd and didn't go far, but it did make it into production.
https://simpleflying.com/boeing-2707-cancelled/