While I see your argument, I think its less likely that Blizzard designed the RDF with Cataclysm in mind. The main reason is, that it took a whole year until Cataclysm release after RDF was released. At the point they started designing the RDF, which was probably a few months before the actual release, they were just getting started with Cataclysm, so its less likely they designed a feature for an expansion, which they didnt know how it will turn out at that time. On the other hand at that time they that saw the needs of players during the first half year of wotlk and tried to find a solution that, which was ultimately the RDF.
I think you could compare RDF to features like dual spec or battleground experience/new queue system.
Dual specialization was introduced in patch 3.1, because they tried to encourage players to play multiple roles for reasons like the tank and healer shortage. Because of the costs of glyphs changing talents had become too costly and a fix was needed, with wotlk in mind.
One Battleground change was introduced in 3.1, the ability to queue from anywhere. The other one, the battleground experience, was introduced in 3.2 to encourage more leveling players to experience more variety while leveling.
In patch 3.3.0, they introduced RDF, because especially while leveling, players had troubles finding groups in time. On low pop servers it was nearly impossible. The ability to queue from everywhere and get matched automatically was the same they introduced one patch earlier in terms of battlegrounds. Its the same for crossrealm matching and the port to the instanced destination and back. Blizzard tried to make the casual content, which is battlegrounds and dungeons, more easy to access during the whole expansion of wotlk.
RDF was not a feature that did something never seen before. It was just a process which elements were already present in wotlk at that point, just for different content.