Honestly, I find it hard to believe that they'll ever take down the shops. On the other hand, the PSP store is already down, DSi went down earlier this year, and the OG Xbox had DLC and such and that is not available too.
BUT
I'd love to see, before end of support, the various platforms offer ways to access patches and such offline.
But so far, all three of those are easily hacked/modded, I just don't know how readily available DSi content is for modchips.