Related noted: I have this persistant inkling that some of the old pain lands (Caves of Koilos, Brushland) are coming back in M15, M16. I'm seeing a bottom-up swelling happening in the prices that are coming either from the invetiable scarcity of nearly a decade of trading and out-of-printness or speculation/knowledge of reprinting (a hunch).
When RtR rotates, Return to Ravnica block shock lands will perhaps briefly lax in price as casual players unload then undoubtedly start a stutterred ascent, to about $15.00-$20.00 apiece by mid 2015, just like the fetch lands from Zendikar spiked to $30 within a year of going out-of-print. I remember kicking myself for not having more that time, so I have 12ish and I will grab a few more if it feels right come the release of Theros block III. I made the mistake of buying 8 of these RtR shock lands mid-season and not waiting for their true bottom, which seems to be close to now, maybe give it until the rotation and see how it goes.
Shock lands are the most like the original duals of any land. They count as two types of basic land. That's huge. They're staples for life.