I think given the popularity of the redone SM in DL, it is inevitable that WDW's will follow suit. And I wouldn't be surprised if it gets refurbed with its current track layout, as this saves them tons of money on R&D.
However, I don't think WDW's SM would take nearly as long to replace as it did here at DL (2+/- years). Given the size of the DL version and it's orientation to the park and nearby freeways, it had to be rebuilt like a ship in a bottle, so to speak. They had to do all of the demolishing and rebuilding using just the small access doors out of sight from park guests.
SM at WDW is a completely different story. It's located outside the berm and has plenty of access from the rear (as far as I know) so the surgery to it could be much more significant, and done at a much quicker rate.
DL's new version of SM has also increased it's hourly rider capacity because it has made the load/unload process much faster. It also has a separate area for handicapped riders to board - the cars can get pulled horizontally off the main track to load these parties while the other cars can whiz by without delay. When the party has boarded the car, it is replaced on the main track and sent on its way. It's VERY cool. It's too bad all rides don't have this feature.
So, I wouldn't be surprised if WDW adds this aspect when they replace the ride system. And for increasing rider capacity even further, I'd rather them keep 2 separate tracks running smaller cars, but maybe doing a DL-style double wide car instead of the single-file WDW style. This would be better than doing one track with a 24-passenger train.