We have less than a week before the servers for the DS and Wii shutdown on the 20th. If you want to do any final trades, transfers, battles, etc. do them now. or just share some memories

>But Pokecheck/PokeGTS don't use Nintendo's servers
The games authenticate through Nintendo first. No authentication means no connection. This has been confirmed numerous times.

>Is there any way to use a fake GTS service after the 20th?
Some modders for Mario Kart Wii are attempting to make an unofficial patch to bypass the authentication, so a similar solution could be applied to other games, but I'm not sure how that would work for the DS games. (flash cart + patched ROMs maybe?)

>Is it possible to import Pokemon after the 20th?
Flash cart or save device. (I'd recommend a flash cart. The R4 is pretty cheap if you just want to put a few games on it and have a DS Lite/phat.)

>Why is Nintendo shutting them all down? Couldn't they at least keep it up for some games?
Gamespot hosts the servers and are shutting them down. Seeing as the service has been running for 10 years, Nintendo probably wants to retire it and focus on the 3DS/WiiU rather than the DS/Wii.