Last date I have heard was Spetember this year, but probably will chanege. In my opinion EEPC v6 have nothing to do with EEFF v4. In other words these two new version will be more sapareted than EEPC v5 and EEFF v3.
I would recommend that you start working with the EEFF v4 beta. The plan is to conduct the beta in June and July, and then target August for the general release of EEFF v4.0. I must add the disclaimer, though, that all dates are subject to change and this is not a commitment to release at that time.