So I talked to Riv. Super nice folks (for anyone who, like me, was looking at them, and lives far away from any dealers). We ascertained that I do ride a 54 which is NOT being discontinued. I actually have a shorter inseam than V - mine is about 29, so hopefully I won't have the problems with the top tube length. Bad news is they're out of them (54's), and they haven't yet placed the next order, so > 6 months for one to come in. Good news: they're still making the 54. They mentioned a TN dealer has one (but it isn't the color I want - it's green and I wanted a blue one...)

Ah well....