There are fundamentally two reasons why Intel is behind on 14nm shipments, the first being sales of 14nm parts still growing faster than Intel can increase capacity,
and water is wet? isn't this the definition for lack of supply? The reality is intel has been super binning it's chips to produce those high clocks on 14nm, in fact they've been super binning since skylake, which means 14nm has always been short of supply because yield has been poor from the very beginning due to the extreme binning they're doing. Now that has improved as the revisions have come, but this shortage is due to the high clock speed demands corperate put on the company, not due to some increased demand for intel processors. call it an artificial shortage caused by 14nm binning. (source? friend who work in the intel fab here in arizona, they also have other information about upcoming nodes too)
the other being 10nm being so many years overdue. If Intel ever manages to get its desperately needed 10nm breakthrough, it'll increase yield per migrated production line by 50+% and solve Intel's supply issues.
unlikely, 10nm was meant to compete with ARM, and when initially conceived was meant to be a low power low clock node with a nice IPC improvement, intel didn't expect AMD Ryzen to actually challenge them so they planned to launch on 10nm with roughly the same performance as skylake, just lower clocks. Ryzen blew up intel's plans for 10nm. It's not that the yields are poor on the node (they're not good mind you) it's that they're unable to clock the chips up much beyond 3ghz without dumping power into the chips, and due to the 3d design, the heat gets impossible to deal with long term. basically it's a node good for making mobile parts not HEDT chips.
We'll see how good 10nm is turning out when the promised desktop Ice Lake finally launches (or fails to) next year. Going to be quite the embarrassment should desktop Ice Lake either show similar clock frequency regressions as mobile parts have or gets delayed into 2021. My bet is on desktop Broadwell-II: technically exists but nearly unobtainable beyond select OEMs.
intel already canceled 10nm icelake desktop chips. it will be a mobile chip only, their next two desktop chips will be yet more 14nm revisions (comet and rocket lake). The plan is for the Golden Cove revision to be on 7nm, and the first desktop node improvement since broadwell and 14nm. Now the plan for 7nm desktop is to release late 2021 to early 2022. the problem is 7nm is a hasty redesigned process, remember how intel was planning on 10nm being an ARM competitive process? well so was original 7nm. They've been redesigning 7nm from the ground up to compete again in HEDT and are on a rushed schedule, so no one knows how 7nm will work, but while certain segments of intel are really hopeful for the process the guys I know here are really skeptical as it's really being rushed right now as intel mostly has given up on 10nm and their original designs for 7nm. They don't think intel will completely right the ship until 5nm.
of course this is full speculation, but when you consider in 2021 AMD will be close to releasing on 5nm, and their 7nm will have been on the market for a year, intel will be really running hard to catch up even if 7nm works.