It very hard to predict sales of Switch at this point, only what I am sure it will sell much better than Wii U, how exactly much better it hard to say, but I can say that at end of 2018. (so less than 2 years on market) will pass Wii U LT numbers.
not really that hard to predict at this point for 2017, it's quite obviously killing it this year, quite possibly will beat PS4 for top console of the year in sales. Going onward is a mystery though as at this point in time we have literally no idea what will be releasing for the Switch in 2018/2019
2017 with FE Warriors, SKyrim, Odyysey, Splatoon. 2017 is settled