Hi Bharath,
v1.6.15 was created from the release-1.6 branch, it looks like [3] was submitted to master. We have the same model as k8s, where new changes to master aren't released until a new minor (ie, 1.7) is cut.
We cut a new minor when there are "significant" changes, which is admittedly subjective and hard to predict.
If your PRs are for minor features, then the easiest thing to do would be to backport them to the most recent minor. You can use github's automatic cherry-pick, by putting /cherry-pick release-1.6 in to the comment thread on your merged PR. That will automatically create the backport PR which is approved in the normal process. Then it will get in the next patch release which should be a few weeks (as there probably will be CVEs to fix).
I'm not sure offhand of the scope of your features and if they're appropriate to backport, I'd reach out to whoever approved your PRs.