Based on the concept art, I certainly expect to see mist screens for projections, similar to what are used in F! (and on a much larger scale, WOC). Water cannons are the hydraulic/pneumatic systems used to shoot water 50-plus feet into the air (as in WOC). I don't expect to see those in RoL; they would have had to drain the river to install them, and it has been established that water table and ground stability issues would not make them feasible for AK.
And for the record, I'm not expecting this to be anything like WOC. The sheer size of WOC is what makes it jaw-dropping. I'm expecting the "awe" factor of RoL to come from the number of components and the overall effect of combining many lighting elements with practical floats, live performers, some fountains, and music. It will be a more "intimate" experience filled with many details that will make it unique (and a good parallel with the park, whose beauty is really in the details). If the quality of the recent DLR night time shows is any indicator, this may well become the best that WDW has to offer.
