Not yet, the queue is persisted by the NS, while the payloads are encrypted by the AS. leaving the items in the queue means that (since these are already encrypted) will give you garbage data. There are some workarounds possible, but I’m not planning to add this to v3.
The upcoming v4 merges the AS and NS components so that queue items can be encrypted on sending the downlink. That makes it really easy to implement a “flush device queue on join” flag 