With all of the issues with processors in the press last week, I can only speculate that there may be new problems with putting these processors in the retail channel.
Also, with the issues with processors in the press last week, I might be inclined to wait for the 9th gen processors (or whatever comes after the 8th gen), if you can wait.
Just speculation and opinion.
I assume that you are talking about the Spectre and Meltdown issues.
In my understanding these are security flaws that will affect performance significantly?
I already have a Z370 chipset and an i3 8100, so I guess that sticking with those and getting the money back for the i5 is the most sensible thing to do?
Is it likely that the Z370 chipset will be compatible with a 9th generation?
I cannot speculate on the performance impact, or what the chipset will support in the future.
I was planning (for myself) to get a new motherboard and processor. However, I will now wait until all of this is resolved, and probably get whatever comes after the 8th gen processor so as not to have any limitations (assuming there are no such problems and limitations after the 8th gen).
My point is that it is too early to know what to do. I understand there will be some patches/updates on Friday, Jan 12 from Intel. Microsoft has already provided updates this past Thursday, and may provide more on Tuesday, Jan 9th.
So, what impact will all of this have? No one knows yet, despite what the press is saying. We need to wait and see what real world experiences say.