The details come via Eurocom, which revealed their Tornado F5 will be updated to Intel Z390; the chipset will support 8C/16T chips based on 10nm+ Ice Lake.
Very unlikely. Comet lake is said to come first for desktop and rumored to require yet another chipset newer than Z390 due to 10-Core power requirements, Ice Lake is notebook only for foreseeable future. At this point though, nothing is certain.
Intel made 8000 series CPUs incompatible with Z170 boards, I'd be surprised if Ice Lake desktop CPUs are supported by Z390 boards. Get an AMD CPU if you want longer term upgrade ability.