Any of those would be good, and I had Super Mario titles for NSO on my predictions list, but I'm not sure at this point.
I definitely wouldn't expect further consoles. They've barely got going with GB on the base tier, and are drawing the releases out with that, and GBA is alternating with N64 on the Expansion Pack tier, further drawing out those two software libraries. Nintendo look to be in it for the long haul with this subscription service and so anything they add now is just content they could use later one, when their options are thinner. There's been a minimum gap of 1 year between consoles being added, so I really don't see Nintendo going 4 months from GB/GBA to the next addition.
A localisation of Binding Blade would be neat and a potentially easy win for Nintendo with fans, sure. I think something lower key like that is more likely today.