It does look like Disney is strategically emphasizing certain projects for both coasts so they can tackle both Tomorrowland's at the same time.
For MK, fully building out the western side of the park will alleviate capacity concerns when you start shutting down and replacing attractions.
- Cars will replace the interest in driving for kids, allowing the Speedway land to be utilized for Fantasyland/Tomorrowland projects.
- Monsters, Inc. at DHS makes MILF repetitive. (I like this attraction, so I hope it's relocated to DHS though)
- Adding a Villains coaster and a Cars (semi-thrill ride) will reduce capacity constraints from a Space Mountain closure.
For Disneyland, I think strategically they need to think through how they plan on using the Subs/Autopia land before expanding to the DL Forward land. It seems like they're emphasizing a build out of DCA first to give them time to figure out/finalize a concept for Tomorrowland. For DCA, it makes sense to expand across the street, but DL has a lot of room to play with in the eastern side of the park first.
Regarding timeline, Disney said everything announced will be opened within 5 years, making 2029 their deadline so we could see something major in Tomorrowland happen as early as 2030.