He has stated since the beginning that as long as people want to play the game, that they have ideas to add to the game, and that they enjoy doing what they are doing that they won't stop developing this. From about 6 years ago:
He's been very up front with this. Also, this is not unlike studios which revisit, revise, recode, reboot major titles.
(EDIT: Also, it's obvious from the interview that his ability to predict timelines and deadlines sucks. No one should have been surprised, especially DC, that his inability to do so would lead to a tech update taking much longer than he initially expected. The man can't predict worth shit.)
You say milking. Patreon subscriptions are for supporting creators in what they are doing, not for product access or product purchase - unless developers say as such. No one needs to pay anything play Summertime Saga. It's available for free to download directly from the developer. The only gameplaying benefit that subscribers get is that they get first access (up to 24 hours before the public) and downloading directly subscriber-only servers. If people only want to play Summertime Saga when there are updates (which were every several months before the tech update but which may not be for another 8 months or a year or more) they can do so without letting loose a dime. If subscribers want to stop their membership, no one is stopping them and nothing is stopping them from accessing the game. How is he milking?