Its not trivial to change an existing software's architecture and philosophy just to be "JSR-170 conform". While its easy to be level-1 compliant (that means certain read-only methods exist), its a lot harder to implement level-2 (meaning you can write data as well).
However, claiming you support level-2 is easy if you just use an existing repository to store some arbitrary data that is generally irrelevant (i.e. you can add jackrabbit to your jars and claim you are level-2 conform while you are not using it).
Marketing-wise, everybody will be JSR-170 12 months from now. (just look at the ridiculous JSR-170 "support" you get with alfresco, jboss portal or websphere).
Thats the problem with all standards - when JSR-168 was final, you could buy JSR-168 compliant portal servers - just that the sales person would tell you " if you use this in JSR-168 compliant mode, you will not get feature a,b, c and e-z".
Of course, openCMS will support JSR-170, too. They will have to or they will die the slow death of an aging customer base. But changing openCMS to truly use JSR-170 is a rewrite of their software.
Here is my suggestion: simply use Magnolia instead.