On May 5, farms 1-5 were expandable to 30x30
On June 1, farms 6-10 were expandable to 30x30
The "track" record of releases has been to expand 11-? at the same time as a new farm is added.
It is quite possible that we will not see a farm #15 for another 3 weeks or so, and then the expansions of 11-15 to 30x30.
However
Last week it was stated that #15 and new levels would be included in the "next release"
confused?

yeah, I am too
Tonight's train stuff might be considered the balance of the June 1 release, and not a real "New" release.... same with the crops and the Thai restaurant.
So, I will just anticipate the restaurant, the crops/trees... and hopefully the start of numerous train items. And I won't plan a theme/design for #15 at this time.
(but I do have 25,000 plots ready for new crop planting, and a number of lots available with all utilities in place for the new facilities)
Trains.... gotta have some trains.