I highly doubt Nintendo will charge you for online, but third parties will.
Let's not forget that in this generation they have introduced two seals for online, blue-free to play and red-pay to play. Remember how Monster Hunter Tri was pay to play in Japan but free to play for the rest? This may be the norm now, with 3rd parties being the ones who decide (so we will have to pay).
Edit: Here are the logos :
FREE
NOT FREE 
Please excuse my bad English.
Former gaming PC: i5-4670k@stock (for now), 16Gb RAM 1600 MHz and a GTX 1070
Current gaming PC: R5-7600, 32GB RAM 6000MT/s (CL30) and a RX 9060XT 16GB
Steam / Live / NNID : jonxiquet Add me if you want, but I'm a single player gamer.







