The comments on that ANN article seem to be unusually (er? At least, I hope so) daft. The SonoHana series is still going strong, and the products announced by Mikajyo (short for Sei Michael Joshi Gakuen i.e. St. Michael Girls' School) are indeed part of it.
Basically, in terms of the status of the SonoHana series:
- It started as an experiment by the doujin circle Fuguriya, which released the first 9 games
- After the success of the series was established, the creators formed the official brand Yurin Yurin (under the commercial company Carnival), through which they released 6 games
- At present, Yurin Yurin appears to have been set aside to establish the new brand (under the same company) St. Michael Girls' School, whose website and twitter account opened this past Wednesday and who currently have two games announced.
Of the two new games announced, one of them is indeed set to focus on a new cast of characters (3 couples unrelated to the existing SonoHana couples), called "New Generation", but the other is backstory for one of the existing pairs from the Yurin Yurin releases. Both are Sonohana games, with existing staff from the past releases.
As for the schlock posted in the ANN forums about the final milestone (construction of an actual, physical St. Michaels Girls' School, in exchange for becoming the most popular/followed account on the entirety of Twitter) being some sort of symbolic/spiritual development, that's just dumb. On the one hand it is obviously a joke offer, but on the other I think they might very well be able to afford construction of a physical academy if they managed to become the number one account on all of Twitter.