Nuls is a very good altcoin no doubt here, they hold a strong place in the crypto industry for a long time. Personally, I like Nuls and EOS technology very much and I think NULS a bit underrated! But I would not call it a next monster, because Nuls development is less and their use cases are not good enough anymore! I will buy NULS coin to make profits because bull run will boost this coin very much, but yet it is not the next big thing, maybe Cartesi, Energi or Insolar will be the next monster!
Cartesi ? 
It is just an upcoming project which for now it will be difficult to predict the future outlook. I think just like op, Everyone will always have this coin they so much have faith in and hopefully NULS wont disappoint just like PundiX