At this time, there isn’t too much known about the deal, other than that the game Super Mario Brothers U Deluxe has been approved for sales in China. It will be interesting to see what other games make it to the Chinese market, or what forms they will hit the Chinese market in, due to the country’s strict censorship laws.
Last month it was announced that Tencent would be working with Marvelous Entertainment to develop a mobile Story of Seasons game. There’s no word on whether this game would be developed in conjunction with Nintendo, but previous Story of Seasons games have been exclusive to the 3DS (with a couple on the way for the Switch), so it could be possible that the two deals are related.
At this time, there is no word on exactly when the Nintendo Switch will be released in China.