Is there a China Narrowbody Order Gap?

Looking at data from ASCEND there is a gap in narrowbody orders from some chinese airlines. Look at China Eastern for example: before they announced to order 50 more B737NG for delivery between 2017 and 2019 their last four B737NG deliveries were scheduled for early 2017. So there would have been a delivery stream gap before China Eastern would get their first of 60 B737MAX in larger numbers.
The same can be said for other chinese airlines:

• Shandong, Shenzen and Xiamen all get their last B737NG this year. Xiamen already announced orders for 70 more B737NG and B737MAX and it could already be included as one from an "Unidentified Customer"
• China Southern also gets their last B737NG this year, so either they also have new orders in place as an "Unidentified Customer" or they will order soon
• Air China ran dry of new deliveries for B737NG's and does not have any (official) order for B737MAX

The same can be said - more or less - for Airbus.
Air China and Shenzen already announced orders for a mix of 100 A320ceo & A320neo and I guess it is already in the books as part of the "undisclosed".
The same is true for China Eastern (70 A320neo) and China Southern (50 A320neo & 30 A320ceo). Some of the A320ceo aircraft subsequently trickled from the "undisclosed" to the China Eastern line of the Airbus O&D sheet. The same is true for Spring and Loong. Spring long ago announced to order 30 more A320ceo and they already might have ordered the A320neo. Also you can see some changes at Tibet Airlines.
The order for 60 A320neo from an "undisclosed asian customer" announced at the Paris Air Show might also be from China. 

Bottom line: the most of the "Unidentified" or "Undisclosed" customers should be chinese airlines. There are probably not much more narrowbody orders to expect in the next few years.