First off, to answer the question, I don't know if Java 8 support will be added to 10.2 M020 via a CPS. I'm pretty sure that it's not out of the question, but I can't say for certain.
Secondly, I should clarify a few things here.
- While Java 8 was released some time ago now, it almost always takes a couple of Java maintenance releases after any initial major Java release for quality to reach the point where one should contemplate moving to it in production. Additionally, it also takes some lead time for PTC to fully test (and fix where necessary) a Windchill release against a new Java client version. Thus while it's unfortunate, it's not a total surprise that M020 did not initially contain Java 8 client support, even though it was released after Java 8.
- As far as "Java" discontinuing support in early 2015, what's being referred to here is that Oracle currently plans to stop providing free maintenance/security updates to Java 7 in April 2015. See http://www.oracle.com/technetwork/java/eol-135779.html#Java6-end-public-updates.
- From my own testing, almost all Windchill applets work fine with Java 8. I did find a couple of features in a couple of administrative applets that didn't work, but that was it in my testing. I'd also note that one has to enable RMI tunneling for Windchill applets to run under Java 8, due to changes Java 8 made to the applet security model. Finally, one still needs the various Windchill fixes and Site Exception List setting that one needed to run applets under the latest Java 7 releases.