Good news: They've started beta testing - So it shouldn't be too long now
That's the first I've heard of it. Really, I think they might want to at least set some boundaries around this. I don't expect a detailed release date where everybody's tapping their foot and looking at their watch. But OTOH, I think if somebody bought 2014 and then 2015 came out say, 32 days later and they had to do a full upgrade I think they'd be a little ticked. If they're getting that close, then just announcing that you can buy without worrying about a full price upgrade they'd generate some good will. I'd be OK with a charge to take into account the hard drive cost as long as it doesn't approach a full upgrade price.
And for those of us who have Windows and Mac and don't want to ditch one, it might be nice to have a bundle discount option.