Are you stating that the ATA186 device has been removed from the system entirely? Other EoL devices have typically remained in the software (e.g. 7940/7960, 7905, even the VIP phones). No engineering support is a far different statement than flat out won't work and requring the customer to buy new hardware.
UPDATE: It appears Payal has redacted his statement. You should speak to your Cisco AM. My opinion here is that you should receive support since the only thing that has changed is UC Manager which is under active engineering support. Get an official statement from a Cisco employee.
As far as I can tell you on my test 8.6 (2a) UCM there is support for ATA186. I mean you can add this kind of device. Anyway I think if I encounter any issue with this devices I will not have support from cisco...