Onkyo just announced this morning their first two 2015 receivers to support the new upcoming DTS:X format (through a firmware upgrade to come later this year). The TX-NR646 and TX-NR747 will offer both 7 channels of amplification for a maximum setup of 5.1.2 speakers.
The other important information is that both will support HDMI 2.0a and HDCP 2.2 at the required bandwidth of 18 Gbps.
As they did with Dolby Atmos last year, Onkyo also posted their detailed information page about the new DTS:X format.
One thing they confirm is that Upfiring speakers / modules used for Dolby Atmos will be compatible with DTS:X.
The MSRP of the TX-NR646 is 699$ in the United States and it does not come with THX Select2 certification and a little bit less rated power than the 747. The receiver will be released early June.
The MST of the TX-NR747 is 999$ in the United States and it is THX Select2 certified. The receiver will be released at the end of June.
Please note that Onkyo did not release at this time any information on the TX-NR1030 or TX-NR3030 replacement models, which are needed to support 7.1.4 playback.