We don't currently have plans to implement renewable or non-renewable purchases at this time.
Replacing the underlying cordova plugin has been on my low priority to do list for quite awhile. That would be the ideal time to reconsider it, but I'm cautious about implementing them after we added consumables. The proper usage of consumables requires quite a lot of forethought and potentially complex infrastructure on a users part, which I expect either stops anyone using it or they just ignore the implications. I'm expecting subscriptions to be similar or worse. A quick look seems to suggest that server side receipt validation is required at least. I also expect usage to be incredibly low, you are the only person who has asked for it as far as I'm aware.
Your free to file a feature request at https://construct3.ideas.aha.io/ideas?project=C3 if there is significant interest we may consider it sooner.
If you need the feature for an upcoming/ongoing project then you may be better served looking into implementing you own plugin.