I am no expert in economics, but all I can say is: it will depend on how much combat is involved in raids 2 and the requirements for it. If raids 2 has the same requirements as raids 1, in which mostly high lvl players will do it, then rigour won't be much on demand, as most of those players already have it.
On the other hand, the rigour price may also be affect by other updates, such as new boss or buff in certain monsters. Vorkath, for instance, bumped the price of the dex scroll significantly, as blowpipe was, at the time, BIS for vorkath. Buff on the drops of revenants also bumped the price of rigour, along with blowpipe and elder maul. For now, I think the dex scroll will be quite stable around the 75M mark, but I cannot tell for sure. All I can say is, keep an eye out of future game updates. If updates benifit range, rigour would probably increase in price.
Just my two cents.