Does percona xtradb support partitioning with foreign keys?
FOREIGN KEYs and UNIQUE constraints that do not include the PARTITION key are complex to implement. Oracle has taken a step, albeit minor, in that direction in 5.7. I would not expect much even in the 5.7 timeframe.
Effectively, you have a choice between FKs and PARTITIONing. FKs can be simulated in code. Partitioning does not automatically provide any benefits. I have identified only 4 use cases, all involve BY RANGE. What is your use case? I would be happy to see if yours is a 5 case, or try to convince you that partitioning is of no use.
The use cases are itemized in http://mysql.rjweb.org/doc.php/partitionmaint