Ok, this has just been announced for Android Netrunner, but it could have consequences for L5R down the road.
In essence, just after the first two cycles are rotated out, a Revised Core Set is going to be printed. This new core set is going to include some cards from the two cycles that are dropped (therefore, reinstating them into legality) but, more important IMO, cards from the original CS that aren't reprinted in the RCS also fall out of legality!
Personally, I'm not against for such a move for L5R in a few years. I never liked the idea of all cards being evergreen with no chance to correct mistakes. First, because at some point we were going to realize that so-and-so card were OP and, while developers could design around that problem for some time, eventually they would be left without design room and would lead to an stagnant playing field. Secondly, from an aesthetical point of view, I didn't like the idea of Champions and other unique characters would continue appearing on the tables years after they were dead in the history.
Frankly, I see no downside to it. "Eternal" legality is not eternal anymore... and I'm OK with that. Call it mono no aware, if you must.
*NOTE: From the info, there are no new cards so you absolutely DON'T need to buy the cards again. Some cards have new artwork, and probably errata will go into the new printings of some of these cards. It simple sets a new standard for what's legal and what's not. If I'm a dedicated player, I prefer seeing some core cards go out (which is happening with the cycles anyways) if that's good for the game.
Edited by Mon no Onitypos, typos everywhere!