Does SQL Server 2016 support foreign keys in an in-memory table from a disk bound table If using an in-memory table in SQL Server 2016, can I define a column in that table as a foreign key from a non in-memory (or disk bound) table? I know that the foreign key does need to be the primary key of the referenced table.

I'm just wondering about the limitations and reliability of in-memory tables and how well they work with disk bound tables in SQL Server 2016.
Does SQL Server 2016 support foreign keys in an in-memory table from a disk bound table

No, not at this time - A foreign key between a disk based table and memory optimized table is not allowed.
You will get below error :

Msg 10778, Level 16, State 0, Line 3
Foreign key relationships between memory optimized tables and non-memory optimized tables are not supported.