I agree that if you can't book (most) of your trips 10+ months out RIV resale is not for you, but I also think it means that all of the DVC at DLR is not for you (because you're paying a big premium to own a DLR resort and they tend to get pretty full well before the 7mo mark), whether direct or resale. The alternative is trying to book way out in advance with current year points and banking if you can't use it, but this is riskier if you can't make it work two years in a row.
As far as how RIV fares after it sells out, I think it may do better for a while but only until Disney announces the next property around Crescent Lake--- perhaps there's a 10+ year window between RIV selling out and when they start to tell people what will happen to BCV/BWV in 2042, but while there are some people who really love Riviera, I see far more people buying it because it's the only EPCOT game in town right now. If do a conversion at YC or a new tower at BC or a front gate resort, I don't think many people are going to be willing to pay sold out resort prices for Riviera direct, which will limit the amount of ROFR activity on RIV resale.