I have no concrete answers, but this was fairly common with the Sync for Reddit app as well. We’d go several months without updates before they’d resume for a while and then drop off again.
I’m relatively confident the same will happen here, so updates will probably return soon^TM .
I see your point - I’m also happy with the current version. That said, I did purchase the app with the expectation of continued development. I’m not demanding major weekly updates in perpetuity or anything, but I don’t feel it’s unreasonable to want reassurance that the app you paid for hasn’t been abandoned a few months after release.
(To be clear, I mentioned in another comment that I know this is normal for Sync and we will likely get more updates down the road. I can just also understand OP’s concern.)