In case you weren’t aware, Japan did not get the NES Classic. Instead the Japanese market got the Mini-Famicom which is more or less the equivalent, except that it appears to be exclusive to the Japanese market. What this means is that the 260,000 units sold are just for the Mini-Famicom, meaning that the numbers could be much higher if we were to take into account the NES Classic.
Unfortunately at the moment Nintendo has yet to reveal the official sales figures of either the NES Classic or the Mini-Famicom, so for now we only have the 260,000 figure to work with. That being said, the consoles are relatively affordable and the games included are pretty classic, so it’s easy to see why there are many who would not mind paying to relive the good old days.
There are no plans at the moment to release more similar consoles in the future, but judging from the response so far, it might not be such a bad idea. Mini Nintendo 64 or GameCube, anyone?