"Don't let them promote you. Don't let them transfer you. Don't let them do anything that takes you off the bridge of that ship, because while you're there... you can make a difference." - James T. Kirk
You only need 10 BNP's for each of the new Mk XII Omega Rep set items, or 5 for the Borg Mk XII's. I'm sitting on over 154 BNP's have can't decide what to do with them lol.
While there is the possibility that BNPs will be used for future sets, that is mere speculation. I suspect that BNPs will be just for Borg Sets and there will be other items for set items for other major enemies like Undine and Iconian. There is the possibility of new Borg sets being introduced, but right now someone only needs 195 BNPs to purchase every Mk XII set unless they want to outfit their Bridge Officers. That would require an extra 60 BNPs. So if you have everything you have at the moment, then the logical course is to use them for dilithium.