The wii's wont be replaced anytime soon. There is still tons of fun to be had with them.
Right now at microcenter we have refurbished systems for $125. These include just the basics, no games. The plain white wii (NIB) is $185, includes wii sports. Both include a standard controller.
The better deals to start off with are the $200 NIB consoles. The black system combo includes console, wii sports, wii sports resort, controller, and the wii motion plus addon required for some games.
The Red console is limited edition, includes wii sports, the new super mario bros (revamp of a classic) and a controller with wii motion plus built in, so it can still be used with attachments. I usually recommend this system the most because the sports games get boring.
Back up games? Not likely. However we sell used games at microcenter, as well as refurbished controllers for pretty cheap if your looking to expand.