If you aspire to make Java into the type of language we would arrive at if we redesigned Java from scratch today, it's not just a matter of adding good features but also removing bad ones.
For example, you'd go directly to Joda-Time or JSR-310. Date and Calendar wouldn't be present at all.
Whether Java should break compatibility to remove all the old cruft I'm not sure. The benefits of the cleaner design might not be worth the costs/inconvenience.
I'm glad you added that last line, because that's basically the whole story. Java is /very/ backwards compatible, and it's got round the...errr...quirks of the early versions by having a massive ecosystem of alternative implementations. Some of these (like Joda-Time) are good enough to get widely accepted as the 'correct' implementation.
I don't think anyone will argue when you say that that throws up some barriers to entry, but they're not massive barriers, the standard library does still work. Not having to rewrite your code every six months is much more important.
Oh, but it's introduced plenty of quirks of its own, which will have to be painfully removed down the line. Odersky himself is trying to redo and simplify the type system with his Dotty project.
For example, you'd go directly to Joda-Time or JSR-310. Date and Calendar wouldn't be present at all.
Whether Java should break compatibility to remove all the old cruft I'm not sure. The benefits of the cleaner design might not be worth the costs/inconvenience.