Maybe you can get some insider info through other non-public channels, but you won't hear anything official from VMware here. That said, while I don't have any access to such information, I'd totally bet that the next major ESXi/vSphere release will support VMDKs larger than 2TB. Judging by the previous release cycles, this will probably be ESXi 6.0 near the end of this year.
I also don't expect this functionality to be added in 5.x through an Update release or something in the meantime.
Btw, are RDMs not an option for your fileserver? You could use a single large LUN this way.