The Oreo update will come when ready. Better to have time to fix many bugs than releasing an unusable ROM...
Its all very well saying when the bugs will be fixed but the source code for Oreo was released in August 2017. Well over 1 year ago. Now the source code for Android Pie has already been released.
To be honest the phone should have shipped with Oreo given the time of Oreo release and phone release. If Blackview say its coming soon then fine wait, but the phone was released 6 months ago so that should be ample time for you to fix any bugs you have found and release it.
If you still have bugs maybe you should relase a beta version to get the community to help find and report such bugs.
If you expect people to continue to use Blackview phones and more importantly upgrade to newer models then you should try to keep the customers happy which includes updating the software regularly.