When migrating from Office365 to Office365 or any other source/target Exchange server; items from the source mailbox folder that has InfoPath forms do not migrate.
There are no warnings or errors in the event log regarding this.
Forward the source data to target
Perform a PST export of the source folder(s) that has/have InfoPath forms and import the PST file into the designated target mailbox
Enhancement requests number, PT107303490 has been submitted to include this behavior as a Known Limitation.